Jul 17

Aquaponics And Water Quality

Water quality is extremely important in aquaponics.  Water quality maintenance is the main chore in aquaponics systems apart from propagation, harvesting and fish care.

Water quality in aquaponics involves careful daily water testing for pH, ammonia, KH, nitrite, nitrate, and oxygen levels, just to name the most basic tests that need to be done. For more details about this, see my articles about oxygen and air pumps and the importance of nitrifying bacteria. This can be done using chemical tests, but it is far quicker and more convenient to invest in hand-held battery-operated water testing sensors which are sold for this purpose, and can be bought directly from this page if immediately needed.

If the quality of your water is not up to standard, immediate action is required.  You cannot expect your fish to remain healthy swimming around in their own waste, and your plants also cannot directly digest the fish waste water, without the intervention of healthy nitrifying bacteria to turn the fish waste products into digested and available nitrate fertilizer.

pH and temperature meter.

The most basic factor is the water pH. This should be maintained using tiny quantities of buffering base materials at a level of 7.0 or neutral at all times. Otherwise things may well start to go badly wrong quite rapidly. Adequate levels of water oxygenation are also vital. You should also know the amount of dissolved solids in your water.

Overfeeding your fish can also badly damage water quality because of uneaten fish food rotting in the tanks. You should carefully calculate fish feeding rates to make sure that just enough feed is being given to make the fish put on weight, without damaging water quality, or also starving your plants in the hydroponic part of your aquaponics system. Aquaponics is an ecology!

Total dissolved solids meter.

Water quality maintenance requires at least a high school level understanding of biology and chemistry. Aquaponics is agricultural science, and as such requires a basic level of education and training in at least the main responsible staff on the aquaponics system.


However, using color coding, which is a common way to design chemical testing materials, even illiterate staff can eventually be trained to use a color coded water quality testing kit to determine if emergency measures have to be taken.  But this should be only a backup measure, to ensure that someone can look after the aquaponics system in the absence or incapacity of the main aquaponics technicians.

If you liked this article, I have edited the first six months worth of articles on this website into the ‘Aquaponics Global Anthology 1′ in printable .pdf format. This can be downloaded immediately here: [paiddownloads id=”1″]

Jul 13

A Crop for Aquaponics: Edible Morning Glory or ‘Water Spinach’.

edible morning glory plant

Edible morning glory plant, ipomoaea aquatica.

An interesting reserve crop for aquaponics, which rapidly fills in for missing plants in plant positions in your grow beds or floating raft system, is the edible morning glory or “water spinach”.  This is a very popular food in the Far East.  Edible morning glory or “water spinach” will grow just by slipping cuttings of it into your aquaponic system. Its botanical  name  is  Ipomoea aquatica, (eep-oh-MEE-uh a-KWA-ti-ka, water loving Morning Glory.) It’s a native of China called “water spinach.” DON’T CONFUSE IT WITH NORMAL GARDEN MORNING GLORY, WHICH IS POISONOUS.  If you do find it in the USA, depending where you live, you’re expected to report it because it can be invasive. Where fresh water doesn’t freeze, such as Florida, it is colonizing the waterways. In northern areas, winter keeps it from spreading. If you are growing it in an aquaponic system, it is difficult for it to spread, since it is contained by the tanks.

There are two versions of I. aquatica, narrow leaf and wide leaf, both are edible. And actually they come in two colors. The “green” version has green stems and white flowers with red throats. The “red” version has purple-tinged stems with pink or lilac flowers with red throats. They both grow only in water, or very damp soil, when not growing in aquaponics systems. The vines, with milky sap, can reach up to 70-feet long (the state of Florida says only nine feet.) Shoots and leaves are the edible parts of your crop. You will not find this plant growing in dry areas.

However, you will be growing this crop to eat as a stir-fry vegetable in an aquaponics system, and will not be likely to see the flowers.  The shoots make up a cut and come again crop, however, as long as you leave an inch or so of stalk and leaf on the plant. They grow very rapidly in aquaponics and can cover your grow bed or floating raft system with a crop of edible shoots in as little as three weeks.  Edible morning glory or ‘water spinach’ is a very popular vegetable in Thai and Chinese restaurants, where you would find a market for your crop, no doubt.

Edible morning glory or “water spinach” is raised as a vegetable in Florida under strict conditions and only for out-of-state sale. It is also grown commercially in Texas, Hawaii and California. In the United States it is found in the wild in (mostly central west) Florida, Hawaii and Puerto Rico. I first came across it growing luxuriantly in the aquaponics system at the University of the Virgin Islands, though I had eaten it innumerable times when living in China and Thailand.

It can be eaten raw when found in wholesome water. The water in your aquaponics system should be wholesome, if you have paid attention to water quality and hygiene around the system.  Fish are cold-blooded, so fish farm waste water does not carry bugs that are harmful to humans (who are warm-blooded), unless humans have introduced them from elsewhere.  Otherwise, edible morning glory or “water spinach”  should be cooked. The leaves are 48% carbohydrates, 24% proteins, 13% ash.  They are rich in minerals and a good source of  vitamins A, C and E. That is a better nutritional profile than a lot of other green leafy vegetables. It is a major food crop and vegetable in its native lands. The roots are sometimes eaten. Like other members of this family of plants, these edible morning glory roots are toxic to horses.

If you like this article, the Aquaponics Global Anthology 1 is available for instant download here: [paiddownloads id=”1″]

Jul 06

The Importance Of Nitrifying Bacteria In An Aquaponic System.



You probably have heard that if you use chlorinated tapwater in your aquaponic system you risk killing all your fish. That’s true, but there are other creatures you will also certainly kill. You can’t see them, but they are there, in your media bed and/or your solids removal and filtration system. These invisible creatures are called nitrifying bacteria.

Yukkk! You are probably thinking that bacteria are all bad, bad, bad. Not so.

You would not be here if it were not for all sorts of friendly bacteria. These are Nature’s cleaning crew. They eat up poisons and waste products and churn out substances that we can use as food, drink, or air.  Nitrifying bacteria are important friendly bacteria.

In the case of nitrifying bacteria living in the filtration parts of aquaponic systems, what they do is eat up ammonia and nitrite and churn out AMMONIUM NITRATE which is what plants need to eat to GROW.

If you kill all these nitrifying bacteria, by putting chlorine, chloramine, or antibiotics in your aquaponic system, you risk KILLING EVERYTHING ELSE IN YOUR AQUAPONIC SYSTEM.

There will be undigested ammonia going around your system, and no nitrate for the plants to eat.

Ammonia, which fish sweat, pee and poo, straight into the water, is toxic in tiny amounts to fish.  If the nitrifying bacteria, which eat it, are gone, it will build up and kill your fish very fast.

There are TWO KINDS of nitrifying bacteria, nitrosomonas and nitrobacter.  Each of these performs a different task in getting that ammonia to turn into nitrate. However, the whole process of turning ammonia into ammonium nitrate fertilizer with bacteria is called NITRIFICATION.


The biological conversion of ammonia to nitrate fertilizer is called nitrification. Nitrification is a two-step process. Bacteria known as Nitrosomonas convert ammonia and ammonium (a different version of ammonia in the water) to ammonium nitrite. Next, bacteria called Nitrobacter finishthe conversion of nitrite to nitrate. The reactions are generally coupled and proceed rapidly to the ammonium nitrate form; therefore, ammonium nitrite levels at any given time should usually be low.

However, if the levels of nitrobacter are low, and nitrosomonas levels still remain high, you may get excess amounts of ammonium nitrite in your system.  This can happen due to overfeeding your fish, and a buildup of ammonia and ammonium due to having undigested rotting feed hanging around in your system. Excess ammonium nitrite causes fish to go down with brown blood disease which can kill all your fish in half an hour.  Therefore test daily for excess ammonia and ammonium nitrite. 

Another indicator of this excess ammonium nitrite situation is if you see your fish refusing to feed and congregating near the surface, gasping for air. Do a 50% water change of the whole system immediately with dechlorinated dechloramined water, and make sure no undigested food and fish mulm is hanging around in the filtration units and grow beds/hydroponic raceways.

These bacteria known as ‘nitrifiers’are strict ‘aerobes,’ meaning they must have free dissolved oxygen (lots of air bubbling through the water in practical terms) to perform their work. Nitrification occurs only under ‘aerobic’ conditions (with lots of air dissolved in the water) at dissolved oxygen levels of 1.0 mg/L or more.At dissolved oxygen (DO for short) concentrations less than 0.5 mg/L, the growth rate of nitrifying bacteria is minimal. Nitrification requires a long fluid retention time, a low food to microorganism ratio (F:M for short), a high mean cell residence time (measured as MCRT), and adequate buffering (alkalinity). 

In other words, the water should not flow too fast through your system to allow the bacteria to hang on to the orchard net, sponge or media you are using as your filter and happily sit there digesting ammonia and ammonium nitrite.  Your aquaponic system should be designed to achieve this in its filtration section and/or media based grow beds. Temperature, as discussed below, is also important, but not really.

The nitrification process produces acid.This acid formation lowers the pH of the biological population in the filtration tank or grow bed and can cause a reduction of the growth rate of your nitrifying bacteria. Since these can take up to four weeks to repopulate your aquaponic system if they are lost due to inattention or other malfunctions, pH maintenance in your aquaponic system is vital. 

The optimum pH for Nitrosomonas and Nitrobacter is between 7.5 and 8.5; most aquaponic systems’ circulating water is adjusted with tiny amounts of lime and potash to stay at a neutral pH of 7.0.   Nitrification stops at a pH below 6.0.The nitrification reaction (that is, the conversion of ammonia to nitrate) consumes 7.1 mg/L of alkalinity, so the pH of the water in your aquaponic system should be tested daily and the levels adjusted when necessary back to a neutral pH of 7.0.

Water temperature also affects the rate of nitrification. Nitrification reaches a maximum rate at temperatures between 30 and 35 degrees C (86oF and 95oF). At temperatures of 40oC (104oF) and higher, nitrification rates fall to near zero. At temperatures below 20 degrees C, nitrification proceeds at a slower rate, but will continue at temperatures of 10 degrees C and less. However, if nitrification is lost, it will not resume until the temperature increases to well over 10 oC.  So watch your water temperature and also make sure it is the right temperature for the species of fish you are raising!

 Some of the most toxic compounds to nitrifiying bacteria include cyanide, thiourea, phenol and heavy metals such as silver, mercury, nickel, chromium, copper and zinc. Nitrifying bacteria can also be inhibited by nitrous acid and free ammonia.  As I said, the chlorine and chloramine used as antiseptics in your ordinary domestic water supply will also kill them.

Water quality in your aquaponic system depends on the partnership between these two kinds of nitrifying bacteria, your plant population, and YOU.

It’s up to you to check and test daily and at every feeding time to make sure that conditions in your aquaponic system are right for all its inhabitants, including the all-important nitrifying bacteria.

Look after these little creatures, and they will look after you, and your plants and fish.

However, if you are in an emergency situation, it is always useful to have these (below) to restart your nitrifying bacteria population WITHOUT a four-week wait-instant nitrifyng bacteria:

If you like this article, I have bundled up the first six months’ worth of posts on this website as an ebook, ‘Aquaponics Global Anthology 1 which is available to download right here for just $10.

Over 30 long chapters of aquaponics advice, how-to articles, and journalism.Aquaponics Global Anthology 1 [paiddownloads id=”1″]



Jun 27

Aquaponics And Conventional Agriculture

Aquaponics differs in many ways from conventional agriculture and other kinds of factory farming.

I have made a chart of the differences between aquaponics and conventional agriculture:

[ws_table id=”4″]

Aquaponics is really green, and can be certified organic if the correct design and methods are used. It recycles at least 90% of the water used and uses far less space to grow far more food for far longer (all year, not just seasonally). Conventional agriculture with its use of artificial fertilizer and pesticide is not sustainable and is an envirommental disaster with long-term consequences which beggar description.

Even organic soil farming cannot compete in productivity with this marriage between intensive fish farming and ‘organic’  hydroponics. However, there are also a lot of differences between the kind of hydroponics practised in aquaponics and the usual methods and equipment used in conventional hydroponics. For instance, the piping is at least 3 inches in diameter in aquaponics to prevent clogging with fish mulm.  Also, no liquid artificial fertilizer is used in aquaponics, while, just likewith conventional agriculture, hydroponics depends on liquid artificial fertilizer entirely.

Just like conventional agriculture, hydroponics eventually vents this artificial fertilizer sludge to the water table with toxic consequences.

No toxic artificial fertilizer residue or effluent is vented to the environment in aquaponics.  The fish solids are composted into organic fish manure which can be used to fertilize field crops or sold on to gardeners. Aquaponic farming is factory farming  of fish and vegetables that recycles nearly everything and processes its own waste properly.  Fish manure is a very popular product!

Unlike other forms of factory farming, aquaponic farming does not produce any unmanageable sewage runoff.  The fish solids can also be put into an anaerobic digester with the harvesting offcuts and composted to produce methane and compost. The methane can be used to fuel a steam boiler and turbine for homemade electricity to run the pumps and air blowers of the aquaponics system.  Factory farming run off its own waste products!

No pesticides or herbicides need to be used, and energy use is minimal.  Staffing ratios on an aquaponic system are very low except for harvesting which requires minim wage piece workers, just like conventional farming, but without the back breaking work of bending.  Floating rafts can be harvested from special trestle tables at waist height!  The conveyor belt planted with vegetables in your aquaponics factory farm has floating raft sections that can be lifted out of the water and placed for harvesting at an ergonomic height.  Even the disabled can work on an aquaponic farm.

This is factory farming with a green twist.

Jun 26

Oxygen, Fish, Air Pumps And Aquaponics.

air stones and air line

Air stones and air line for commercial aquaponics

Fish do not breathe water.  Fish breathe oxygen dissolved in water.  They need that oxygen constantly, day and night.

If you turn off the regenerating air blower that pumps air through the air lines in your aquaponic system, you will lose all your fish within the hour most likely.

This is because the fish will suffocate if you turn off the air pumps.  They need the air provided artificially because they are in tanks in an aquaponic system in large numbers.  The natural diffusion of air into the water is not sufficient to keep them alive without large amounts of supplementary air being added.

Fish stocking densities in commercial aquaponic systems are high. Commercial aquaponics can stock at a tilapia fish per gallon or 600-1200 fish in a 7.8 cubic metre tank, depending on the final grown size of the fish.  Red tilapia come out smaller after 24 weeks than Nile tilapia and so can be stocked more densely. They need high oxygen levels at all times!

But this intensive rearing of tilapia will fail suddenly if there is no air being pumped into the tanks. It reaches the tanks via air lines full of air.

Regenerating air blowers or ‘air pumps’ have to run 24/7 to provide this air.  Oxygen levels in the water in your aquaponics must remain high at all times. You therefore should be able to afford the electricity to run these pumps constantly and also have backup pumps ready to go immediately should something go wrong with your oxygen levels or if one of your pumps breaks. You cannot turn off the air pumps at night because fish need to breathe at night, too!

Your plants also need air in sufficient quantities to the roots in the water column, so air pumped to the hydroponic raceways is equally important.

Without sufficient oxygen, all the living things in your aquaponics will die. Don’t turn off the air pumps!

A good idea is to buy a dissolved oxygen meter, see opposite, to daily test your actual dissolved oxygen levels. A concentration of 5 milligrams per litre is recommended for optimum fish health. Some species such as trout require more, however.

All that air fizzing through your tanks also helps to keep fish solids in suspension so they are carried out of the tank constantly by the water flow to the solids removal section of your aquaponic system.

If you are worried about electricity bills, you should investigate installing alternative energy generation equipment on your aquaponic farm such as a concentrating solar power system, which will provide electricity from the sun even at night, unlike solar panels, which only work in the daytime.

Another option is to use the farm organic waste such as fish solids, dead fish, and plant offcuts from harvesting and so on, to fuel an anaerobic digester.  This uses bacterial action to ferment the organic waste from your farm into methane gas, which is collected, compressed, and used to run a steam boiler which generates steam for a conventional dynamo, running day and night. This will give you enough electricity to run your pumps constantly, as long as your digester is big enough and calculated to be the right size to provide the energy required.

To run the right size digester, you will have also to be able to find the right amount of organic waste, however, at all times.

All of these energy calculations are something you should do first before even constructing your aquaponic system.  If you run out of energy, your fish will die from lack of oxygen, since the air pumps will stop pumping and the water will go stagnant very fast.  Stagnant water is a death sentence to aquaponics!

Before embarking on aquaponics, always work out how much electricity you will need to use.

If you like this article, I have bundled up the first six months’ worth of posts on this website as an ebook, ‘Aquaponics Global Anthology 1‘ which is available to download right here for just $10.

Over 30 long chapters of aquaponics advice, how-to articles, and journalism. ‘Aquaponics Global Anthology 1′ [paiddownloads id=”1″]

Jun 24

How Many Fish Can You Grow In An Aquaponic System?

University of the Virgin Islands commercial tilapia aquaponics system

University of the Virgin Islands commercial tilapia aquaponics system

I keep being asked, “How many fish can you grow in an aquaponic system?”  The answer depends on how much space you have to grow fish and vegetables.

The number of fish you can grow in an aquaponic system  is limited by the number of vegetables you can grow to balance out the system biologically.  There have to be sufficient plants growing in the aquaponic system to soak up all the nitrates excreted by the fish.

See Murray Hallam’s short video below which explains why you cannot just use your swimming pool and throw in a load of fish and pipe the water around to the hydroponic part of your aquaponic system.


The University of the Virgin Islands system, for instance, is on an area of 0.05 ha. It  has four 10 foot in diameter tanks rearing tilapia fish in series each one with a total volume of 7.8 cubic meters. The total volume of fish in water at any time is therefore 31.2 cubic meters . The fish are in the fish rearing tanks of the aquaponic system for 24 weeks. The tanks are stocked with fish at a small fish per gallon, each tank being stocked in series, so they can be serially harvested, and the fish are left to grow out. Remember that the fish put on weight during that time and are harvested when they reach around one and a half kilos each. This is very intensive fish rearing and the tanks have to be constantly artificially aerated or the fish would die.

These tanks use water which is recirculated constantly through the gravity-fed solids removal and degassing section and then the liquid waste flows down to six hydroponic raceways which cover most of the rest of the site. Each of these hydroponic raceways contains 11.3 cubic meters of water. The total volume of water in the system is 110 cubic meters. The total amount of water in the hydroponic section of the system is 67.8 cubic meters. However, the water in the solids removal and degassing section amounts to a further 11 cubic meters which is not accounted for in summing together the water volume containing fish and the hydroponic volume containing plants. All this water is constantly being recirculated round the system day and night and provided with adequate amounts of air. Solids are regularly removed three times daily.

These raceways are four feet wide and two deep. The water circulates through them and these raceways are also constantly aerated. The plants grow suspended in net pots in floating rafts that float on top of the water.

The surface area under plants in raceways is many times bigger than the surface area of the fish tanks. However the volume of water in the hydroponic section is not substantially more than double the volume in the fish tanks, which is adequate to remove dissolved nitrates from the water AS LONG AS ALL PLANT SITES IN THE FLOATING RAFTS ARE FILLED AT ALL TIMES WITH GROWING PLANTS.  The total plant growing area is 214 square meters, but plant site spacing is considerably closer than in soil, since plant roots do not need to grow sideways to find nutrition.  Adequate nutrition is directly supplied by the flowing fish waste water. So many more plants can be grown per meter than in soil and planting density is high.

This high planting density is also a factor when calculating how many fish can be supported comfortably by the aquaponic system.  Many more fish can be supported by aquaponic system fish tanks than can be supported by an equivalent volume of fish rearing pond water. When stocking Nile variety tilapia in the University of the Virgin Islands system, the stocking rate for Nile tilapia is 77 fish per cubic meter, harvested every 6 weeks on a 24 week cycle between the four tanks.  The stocking rate for hybrid red tilapia in this system is higher, 154 fish per cubic meter, harvested every 6 weeks in the same way on a 24 week cycle. That means the fish go into each tank as fingerlings at the above rates and stay there to grow and put on weight until they are harvested 24 weeks later.

How many fish can you stock in each tank? For Nile tilapia that is 600 fish per tank, and for red tilapia, which are smaller, 1201 fish per tank. AS LONG AS YOU HAVE THE CORRESPONDING AREA OF HYDROPONIC RACEWAYS STOCKED TO THE MAXIMUM AT ALL TIMES WITH GROWING PLANTS.  The aquaponic system fish waste water is cleaned by the plants. How many fish you can grow is basically determined by how many plants you can pack into the raceways and have growing robustly. The water has to be flowing round the entire aquaponic system at all times and the air blowers have to be pumping air into the system via air lines and air stones in the tanks.

Fish growth is also affected by water temperature.  Tilapia fish are tropical fish, and will die at temperatures below around 20 degrees centigrade. They also start to suffocate at temperatures over 30 degrees centigrade, which is why their area is in a shed, see the above picture.  The shed provides shade and prevents too much sunlight reaching the tanks and causing algae to grow.  The Virgin Islands are in the Caribbean, and are tropical, so there is no need to heat the water, but in temperate or torrid desert conditions controlled climate greenhouses and additional fish rearing tank temperature control are necessary.

Also, tilapia are robust fish and really tolerate far more intensive stocking conditions than many other species of fish, for instance, trout.  For many other species of fish stocking rates should be at around 30 fish per cubic meter or even less. Rearing periods for fish such as trout and perch are not 24 weeks, but more like 2 years from fry to plate size in each tank. There are species specific conditions that have to be observed, for instance, trout are cold climate fish and prefer temperatures below 20 degrees centigrade, but above 10 degrees. For my article about rearing brown trout in aquaponic systems, see http://aquaponicsglobal.com/?p=162

Trout require much more fussy water conditions than tilapia, too, but trout water still produces bumper crops of vegetables.

You just cannot grow nearly as many of them in an aquaponic system as you can tilapia.  And they grow more slowly.

An aquaponic system is a calculated balancing act between the number of fish and the number of plants it contains.

Jun 20

Aquaponics And Green Walls

green wall

Vertical green wall construction

Ornamental green walls on buildings have got quite a bit of attention recently. I was trying to get into the Queen’s Jubilee parade recently in London when I came across one of them on Park Lane, near Marble Arch.
Of course, everything growing up the building was ornamental, not edible.
It occurred to me that there are thousands of square miles of indifferently insulated external walls on high rise buildings that could be adapted fairly cheaply to growing EDIBLE aquaponic green walls.  These could easily be watered in a cascade system recirculating water from the bottom to the top of the building, using waste water from fish rearing tanks on the roof and/or in the basement of the building.

All you would need would be a couple of low-wattage aquaculture pumps such as the Sweetwater range. This would take urban farming to a new level, installing aquaponic farms all over vertical and near-vertical surfaces all over the city.

Systems of suspended platforms similar to what are already used to clean windows on these buildings could be used to harvest the crops from the aquaponics green walls.

Climbing squash

Climbing squash

Bumper crops of vining plants such as bean varieties, including soybeans, tomatoes, peppers, melons, squash, strawberries, passionfruit, and so on could be got off these vertical  surfaces. Aquaponics marries aquaculture and hydroponics, and green walls are a form of hydroponics gone vertical, which can definitely use the waste water from fish farms for nourishment for these crops.

The rooting surface would be a thick layer of coir (coconut fibre) matting stapled under a plastic mesh. The water would be piped to cascade down the building’s sides through the coir matting, to be collected in gutters at the bottom. From there it would flow using gravity to a sump to be pumped back to the fish tanks.

The usual aquaponic filtration units would stand between the fish tanks and the vertical green walls, to collect fish solids that would otherwise cause clogging and odour problems.  The plants would take up the nitrates from the fish and the water would go back to the fish tanks clean, to be reused.

Vertical hoop houses could be installed to provide winter cover and extend the growing season on the edible green walls. In tropical urban farms on these vertices, winter protection would not be necessary.

Solar and wind energy could be used to power the pumps, based on the roof.  This can be tied into heat pumps recycling heat from inside the building, heat going to waste from air conditioners, etc, which can be used to heat and cool water and hoop house interiors.  Hoop houses can be low rise, ie vertical and only the height of the crops. They can unclip in sections from the walls to give access to the crops. The crops will be living off waste heat from the building and giving back the energy as food grown in aquaponics.  The green walls will also help to stop heat from escaping or entering the building in excessive amounts.  Urban farming in this way will also contribute to the total energy economy of a building.

runner bean

Climbing runner bean

In this way, the thick layer of coir matting and vegetation would also help insulate the inside of the building, and balcony gardens could also be part of the system.  Shade could be provided for those walking beneath as well if needed.  Marginal housing estates with little level garden space could convert themselves to thriving community vertical aquaponic urban farms. Urban farming could rescue whole areas from inner city blight.

Whole city districts might eventually be mostly covered by a layer of edible food trellis gardens apart from near the street level. Because food would be produced locally for local consumption using this method of urban farming, the costs passed on to the customer to pay for food transportation from distant farms would be eliminated.  Urban farming farms the food right next to the food consumer, and the consumer of this food does not have to pay high food prices with the cost of importing food included in the price.

This would completely change the character of cities and provide jobs maintaining the locally grown food supply for people who at present may not even be employed, with training and on the spot apprenticeships in vertical farming freely available to local people.

Aquaponics is a very flexible technology that can be adapted to all sorts of sites, as long as the biological balance between fish and plants in the system is correctly maintained.  Plant growth in aquaponics is usually much faster than in soil, so that maximum advantage can be taken of all the space under aquaponic crops.  Plant spacing is usually less as well, since plants are fed direct to the roots and do not have to stretch out root mass to find nourishment.  With some crops such as basil, it is possible to grow twice as much twice as fast, and the yields go on all year without seasonal rests.

red tilapia fish

Red Tilapia ready for sale

As far as species of fish in aquaponics are concerned for this kind of scheme, it really depends on whether your building has enough waste heat available for maintaining tropical species, or not. Tropical species of edible fish such as tilapia require constant water temperatures of 20-30 degrees C.  Trout and carp varieties, including ornamental koi carp, thrive best between 10-20 degrees C.

Tilapia grows from fish fry to plate size in 6-7 months, whereas most other species of fish take two years to reach a decent size. If your fish are also going to play an ornamental role and be visible to the public, this may also be a consideration when choosing a species to raise on your roof and/or in your basement. Of course, some species of tilapia such as Mozambique or red tilapia are ornamental cichlids as well as edible culinary fish. Tilapia species are robust and do well in aquaponics. I would recommend them at least to start with, as they are a bit more human error tolerant than say, trout and are less likely to die in protest if you make a few mistakes.

University of the Virgin Islands aquaponic system fish rearing tanks

University of the Virgin Islands aquaponic system fish rearing tanks

The aquaponics green wall possibilities are endless. It’s really up to you.

Jun 15

Aquaponics – Your Community Food Bank

By getting together with other members of your local community to exploit unused spaces such as back lots and rooftops, along with waste heat and water from buildings and also food waste from restaurants and institutions, you can build integrated aquaponics systems into your area that will serve as a permanent food bank in these hard times.

You must have seen the film clips in which desperate people sit on street corners with notices saying “Will work for food.” Well, with a community aquaponic farm in place on one or several sites, people can work for food and also for other things like valuable experience and social networking on the farm.  When your farm is finished and in full production, excess food can be sold to pay a living wage to the stalwart workers who have helped to make it all happen. You may find that the farm very rapidly outperfoms expectations as a local food bank.

Building an aquaponic system can either be a million-dollar large commercial enterprise made of state of the art technology, or it can be just as sophisticated, but built out of recycled materials garnered from skips and building sites, and friendly donations of bags of concrete and rolls of LDPE pond liner.  You will need to build tanks and these can be cobbled together successfully in a variety of ways. Aquaponics is always a stimulating design challenge, but with so many successful systems like the University of the Virgin Islands type aquaponics system already proven to work, it is better to follow their lead rather than reinventing the wheel!

If you are going to use wood in aquaponics system tank construction, you should make sure it is sound and thoroughly termite and rot proofed before it is incorporated into any tank structure.  Also be very careful about copper sulphate compounds that are routinely used for rot proofing wood.  These are lethal to fish and plants.  So any such treated wood must be painted over with a non toxic paint as well to make sure the water in the system is not contaminated with copper!  If you can, use steel pipes and galvanized heavy duty welded fence wire in tank construction rather than wood for your aquaponics system. That way you avoid your tanks rotting and breaking before you can harvest the fish inside. Wood can break your food bank!

Do not use any copper pipes or implements when doing aquaponic farming.  Copper pipes and wires may be all right inside your house, but copper is a fish farmer’s and hydroponic farmer’s nemesis. Avoid it at all costs.

Fish are very sensitive to any heavy metals and will die if their water is in continuous contact with any of them (copper, lead, silver, rusty iron, and so on). When building your aquaponic food bank, remember this is not at all just book learning. You are working with living, breathing creatures who have minds of their own.  Fish and plant wrangling can be stresssful since a food bank of this sort is also a living species bank!

Various means can be used for heating and pumping water, and for creating the energy that will run the air blowers you will need to make a success out of intensive fish and plant raising on a commercially viable scale.  One of the cheapest ways of building your own power station is to build an anaerobic digester or series of digesters.  These make methane out of farm and human waste, which is ‘cooked’ by airless fermentation inside a large concrete vessel.  The resulting methane gas can be compressed and used to fuel  boilers for hot water and steam for electric turbines.  These days self-assembly anaerobic digester kits which do not need anyone with an engineering degree can be got for reasonable prices from China.  For further details, look up ‘anaerobic digester’ on http://alibaba.com.

Anaerobic digestion also gets rid of farm waste which would otherwise create a health hazard fairly rapidly.  This makes sure that your community live food bank is not also a toxic waste dump.  Ensuring your own food security should not entail creating a stink!  You need to get off the grid with your energy supply in any case, since an aquaponics system uses modest amounts of electricity 24/7.  You do not want your food security to be impacted by enormous electric bills.

Before going ahead and raising fish, find out which fish are popular already in your area and raise those.  It will be the vegetables raised in the fish waste water that make most of your profits, since fish take anything up to two years to get to plate size. So for the first couple of years, until you start harvesting your fish tanks in succession, you will be making your living off the plants, not the fish.  The fish will be too small to eat for most of that time.

Make sure that your fish tanks are seeded in succession so that you get a harvest of fish say, once every six weeks once they start to come on line. Work out how many tanks you will need to get that harvest coming in year-round, and how many vegetable raceways you will need to balance the nitrates in the system.  This is a complex calculation and will be referred to in my next How Much Fish Can An Aquaponic Farm Raise? article.

The nature of your community and the level of its commitment to farming locally and sustainably, creating local food security, will directly affect the size and success of your community aquaponic farm. You need to establish routines and standard operating procedures and stick to them.  Your local markets for your produce and fish will also have to be weaned off imported and artificially fertilized produce bit by bit. You can also expect to see an increase in the organic waste offered to your anaerobic digesters for recycling. This is free fuel for your aquaponics system power plant.  Food security depends on energy security, so training your local community to route organic waste to your digester should be a top priority in marketing your aquaponic community live food bank to all concerned..

Because aquaponic farms, properly designed and managed, can produce up to four times more food than an equivalent conventional farm on the same area, for far less inputs, you may eventually find that you can actually feed a lot of your local community members almost entirely from the produce, fish, and other food enterprises that you local community aquaponic farm has put in place.   For the food security your own community live food bank will provide over many years to come, everyone has to make a commitment to keeping up the pace of work on the aquaponic farm.

Jun 10

Aquaponics For Schools

lettuce seedlings in the UVI aquaponics system

Lettuce seedlings in the UVI aquaponics floating raft system.

University of the Virgin Islands commercial tilapia aquaponics system

University of the Virgin Islands commercial tilapia aquaponics system

To any ambitious biology or business teacher, a small commercial aquaponic farm is a priceless gift.  In any large flat roofed school building, you can have one on the roof and the students can run it as part of their classes, since it is automated largely.  But keeping an eye on the aquaponic organic food factory on the roof will teach them more about real biology, farming and agribusiness than any number of textbooks.

It may also provide the school with a much needed source of income in these interesting times.

But what is aquaponics?  Aquaponics is intensive fish farming in tanks married to intensive vegetable farming in tanks.  So you should know all about fish and plant biology as it applied to intensive aquaculture and hydroponics. This gives your students first-hand experience of looking after a natural ecosystem in an artificial container.  You also should know how to keep the water quality good enough to suit the plants and the fish. Chlorinated water cannot be used, since the disinfectant in the water kills the bacteria that make the fish waste into plant food, see the diagram below.

aquaponics flowchart

Aquaponics system biology flowchart

Fish excrete ammonia. Nitrifying bacteria in the filter part of the aquaponic system convert the ammonia to nitrates.  The nitrates are absorbed by the plants, and the plants grow really fast. This makes the water clean. The water is pumped back to the fish to be used again.

In aquaponics, only 1.5% of the water is lost in a properly designed and run aquaponics system. So it is very good for saving water on the farm. In aquaponics, plants can grow up to twice as fast at half the usual spacing. So you get up to twice as many plants, twice as fast, compared to farming in soil. But this can only be done if you have the right aquaponics system and the right training. As with any business, proper management is very important.

You will also need to know how to run and clean water pumps, air blowers, and alternative energy sources such as wind and solar generators.  You need a cheap source of electricity to run the machinery of your automated aquaponic food factory on the roof.

YOU DO NOT NEED SOIL IN AQUAPONICS. You only need water. And you do not waste any water.

Because you do not need soil, only tanks of water, you can do aquaponic farming anywhere, like on the school roof, as long as you have electricity and somewhere to put the tanks, the pumps, the air blowers, and the plumbing.

In the tropics, you do not need a permanent greenhouse, though in places like Hong Kong where the temperature goes down a lot in winter, you will need temporary plastic hoop houses to cover your aquaponic systems and also to protect them from typhoons. These have to be quite strong to keep the wind and rain off the system. For example, lettuces do not do well in temperatures below 10 degrees centigrade and above 20 degrees centigrade they start to die.

Pictured below is a gravity feed version of a small aquaponic system. You would need something larger than this to make the farm economically viable, but this give you a basic idea of what can be done with recycled materials and a tank or three.

Usually the first fish you use to make the fertilizer for your plants is the tilapia fish from the Nile originally. It is one of the most commonly farmed fish in the world. It is a tropical fish and does not stay alive in water below 19 degrees centigrade or above 30 degrees centigrade. You will need someone on your team who has kept tropical fish before and knows how to look after them!  If you live in a cold climate you will need to have some equipment to heat the water to the proper temperature and keep it that way.

Tilapia fish

Tilapia fish

gravity feed aquaponics system

Gravity feed aquaponics system

No fertilizers or pesticides can be used in an aquaponics system. They kill the fish! Instead, the fish water contains the nutrients that the plants need, and the pests can be controlled using biological methods.

Biological pest control methods include using friendly insects such as lady bugs to eat up all your aphids, also called greenfly.  There are also parasitic wasps and lacewings which also eat other pests as well. You can buy these online and they come in suspended animation in little blister packs. You spread them out with a camel hair paint brush so as not to damage them, and lift them onto the areas where the bad insects are eating your crops. That’s it!

Another way to get rid of pests such as caterpillars is to use a bacterium called bacillus thuringensis. This comes as a white powder which you spray on. It makes the caterpillars sick so they die, but is harmless to fish and people.

Here are some aphids and the ladybugs that like to eat them:


Aphids eating a plant



Ladybugs, ladybirds

You can also use harmless fats and oils to drown the insects that are eating your plants. But no insecticides or pesticides. They really do kill the fish, even if they are labelled ‘organic’!! You can be sure that none of the children will get poisoned by aquaponics for schools.

There are no weeds in aquaponic farming systems, so you do not need to use herbicide. So aquaponics for schools is not a toxic or dangerous activity.

There is no digging in aquaponics, and you can put the grow beds and raceways for the floating rafts up on tables and stands, so even people with bad backs can and do farm with aquaponic systems.

You can do all the work you need to do, including regular testing of the water to make sure the pH and other factors are correct, in a few hours a day. Your aquaponic systems are low tech mechanical systems with fish and plants growing in them. You have to make sure the fish and the plants have the best growing conditions. This sometimes means adding garden lime or potash to the water in tiny measured quantities to make sure that the water stays at a pH of around 7.0, or neutral.  This is something to do for your biochemistry classes. Looking at the kH and hardness of your water supply and other features of water quality analysis will give them lots of practical experience of how classroom work applies in the real commercial world of fish farming and modern recirculating aquaculture.

But before you go ahead and construct your own school aquaponics system, you need to look at all the business side of aquaponic farming in your area and do a business plan. If you cannot sell your fish and vegetables, you should not grow them!  Aquaponic systems can produce up to four times as much food for the space used, compared to conventional soil farming.  1/16 of a hectare of rooftop space can produce around 5 metric tons of fish and up to double that of vegetable plants a year. That is a lot of food to not be able to sell locally!  Schools that have their own aquaponic systems need to be sure that they are not going to have a lot of food that is simply rotting on the roof.  This is also very intensive fish and vegetable farming.

Market research is the first thing you do when you want to start a business, and aquaponic farming is a business. Aquaponic systems are very efficient food factories if properly managed and operated. This is something really interesting to do for your business class as a project. From your market research in local shops, markets and restaurants you can work out how much food you need to grow to cover the expense of constructing and operating a commercial aquaponic farm on the roof of your school. So then you can work out if there is enough room on your school roof for a big enough farm to cover your costs and perhaps make a bit of a profit. Aquaponics for schools is not aquaponics for fools!

If you are considering this kind of small commercial aquaponic intensive fish and vegetable farm on your school roof, please get in touch with us here

Call me! - Charlotte Appleton: Offline

» Get Skype, call free! and we can help you set this up correctly over Skype for a reasonable fee. If your farm is very big, it might be worth your while for a consultant to come and oversee the installation of your farm and the first few months of the business.  Aquaponics for schools can become aquaponics for whole communities.  If you get the whole community involved in their intensive fish and vegetable farm on your school roof, the sky is the limit!

Aquaponics Global Anthology 1 is available for instant download and to print out here: [paiddownloads id=”1″]

Jun 10

Aquaponics, Arcology, And Sustainable Development.

Aquaponics, correctly constructed and managed, is an essential part of sustainable development. Aquaponics is intensive fish farming in tanks married to hydroponics in tanks.  The reason that this has to be in tanks, not ponds, is that the tanks and associated plumbing and pumps allow much more intensive fish and plant production with close scientific water quality control. Also the water usage of an aquaponics system can be closely monitored and controlled to achieve water exchange rates of only 1.5%.  The water exchange rate is the water that has to replaced in the system when it is filled and pumping.  This compares favourably with water usage in conventional farming where the water exchange rate in an irrigated field is close to 100%.

floating raft aquaponics system

Simplified diagram, floating raft aquaponics system.

Water loss is minimal in aquaponics, which is a recirculating aquaculture system for both fish AND commercial crops. Food yeilds per hectare can be up to four times that of conventional farming, using far less expensive inputs, with proper trained and experienced management. Little ecological footprint is involved and pollution is not generated, since all nitrates are removed by the plants in the rafts, and the water recirculated to the fish in a clean reusable condition.

Aquaponics is now leading the way in successful urban farming enterprises in the United States such as Sweetwater Organics and Growing Power in Milwaukee, Wisconsin and Greater Growth in Knoxville, Tennessee.

As part of an arcology,aquaponics becomes a way of sustainably feeding thousands of people as a designed-in feature of the vertical self-sustaining city of the future.  Water is lighter than wet soil, which means that the floating raft aquaponics system as pictured above is suitable for including in buildings without so many of the crushing weight load problems associated with raised bed soil gardens. These urban farms can also yield over a million pounds of food on 1.5 hectares, as with the documented Growing Power urban aquaponic and sustainable farm in the city of Milwaukee. A picture of the floating raft system at the University of the Virgin Islands commercial aquaponic farm is included below.

Lettuce crop in floating raft aquaponics system

Lettuce crop in floating raft aquaponics system, UVI.

In the sustainable development of the city of the future, food security remains an urgent issue. Cities need to be unhooked from addicition to oil and gas, and the arcology requires no cars, as aquaponics requires no fertilizer or expensive pesticides and herbicides. The fish and pumps do most of the work!  As a plumbing system that sustainably produces food, aquaponics can easily be included in the modern arcology. This makes the sustainable development of a city that produces its own food with few inputs from outside very easy.

The best-known proponent of arcology urban design is the designer of Arcosanti, an arcology being built in Arizona, by the famous architect, Paolo Soleri.  He has developed and personally applied many of the design principles of the modern arcology. Another of his arcology designs is pictured below. There is easily space inside for a few large scale commercial aquaponics food factories and urban farms.

arcology soleri

One of the arcologies designed by Paolo Soleri


Model of an arcology with built in farm on roof.

The tank systems for the hydroponics and the fish farm can be built in to the design for the water and waste management systems for the arcology. As part of the atria inside the city, they can also be modules in the ornamental indoor park area features, with all of the plants both ornamental and edible, as a pick as you go salad bar for the population, who also maintain the public aquaponic farms with their floating raft beds of vegetables and associated intensive fish rearing tanks, on the various levels of the building.  Anaerobic digesters and wicking beds complete the picture, digesting organic waste and circulating the waste water from that as irrigation water for wicking beds that are used to grow root vegetables such as potatoes and carrots, that do not do well in floating raft systems.

A diagram of a wicking bed with its piping for the flowing waste water from the anaerobic digester is below.  It uses waste water from the anaerobic digesters.  It also uses digested solids that have been worm composted subsequently as the growing medium, thus returning organic waste at this last stage of processing to the state of edible food.  These design principles all hinge on recycling everything in the city through long cycles that safely transform organic waste back into food, water, and usable fuel.

wicking bed

Wicking bed-irrigation from below

Anaerobic digester power plants are also  a way of recycling water from waste management systems (such as sewage collection pipes). It is important to realize that all the organic waste, whether human or animal, fish or fowl, and all the vegetable and food waste, represent proper fuel for the anaerobic digester systems that produce methane gas that can be used to fuel boilers for hot water, heating, and steam generation for electricity producing turbines. This means that the aquaponic farm is a part of a sustainable development of a city which uses its own waste organic matter to generate both food and energy. Aquaponics is a very important technology in environmental engineering.

Waste solids from the anaerobic digester power plant are safe to use since they have been ‘cooked’ by the heat generated by the digestion process.  These solids can be further digested by using the worm composting method in large compost bins, and then used as the growing medium in the wicking beds, see the diagram opposite.  Many root vegetables, which have  a high nitrate fertilizer requirement, simply thrive in worm compost of this high quality. No digging is required in wicking beds if the upper portions are made of easily removable narrow gauge galvanized chicken wire or similar tacked to supporting posts with removable ties.

All of these technologies can basically be put on castors with wheels, and used like furniture in ‘food factory chambers’ in an arcology. Alternatively, the tanks and beds can be plumbed into the design at the outset, with all the factors calculated so that they meet the nutritional needs of the tens of thousands of people. Urban aquaponic farms and aquaponic farm parks will be a normal part of the pedestrianized environments of the near future’s new arcology urban neighbourhoods. Environmental engineering is very important in arcology design.

In an arcology, everything you need is in your part of the urban vertical stack, only within 20 minutes’ walk of where you live. There is no urban sprawl, the city extends upwards, if you need to go up a level, you walk up stairs or take the lift.  You do not need a car. The urban design has done away with the need for extensive road networks. Your neighbourhood is also your job, you participate in its maintenance and grow food with your community in your own area of the building, in a farm that is also a water pumping machine.

Light for the atria is brought into the building via lightwells with reflecting mirrors.  Low-energy restricted wavelength grow lights can be used on crops to increase the day length and speed of growth, fuelled by electricity which is made from organic waste from the city, its farms and restaurants. Solar collectors and wind-powered generators on the outside of the building also contribute to meeting the energy needs of the city’s inhabitants.  A city a thousand feet tall generates a lot of wind.

We at Aquaponics Global Ltd are available to assist in building the commercial aquaponic farm sections of any such civil engineering and architectural design and construction contracts.

anaerobic digester

Anaerobic digester methane tank, upper portion


Aquaponics Global Anthology 1 is available for instant download and to print out here: [paiddownloads id=”1″]