In your aquaponic farm, you have live fish.  These fish excrete ammonia through their gills into the water, and a certain amount is also excreted when they poo.

All this is going on all the time. Fish are not fussy, they just do this all the time all over the place.

Since you are farming fish intensively, this represents an awful lot of fish solid and liquid excreta that you simply must get rid of immediately.

The reason it has to be dealt with immediately is that if the ammonia is allowed to build up, it will kill all your fish.  Ammonia levels in your fish tank water must be kept as close to zero as possible at all times.

Then there are the breakdown products of ammonia, nitrite and nitrate.  In a healthy tank, levels of these two substances, caused by the breakdown of ammonia in the water by free swimming nitrifying bacteria, should also be as close to zero as possible.

If the nitrite levels in your fish tank water reach too many parts per million, your fish will start to die.  If you do not get to them within a few minutes of these levels going too high, they will all be dead within half an hour of irreversible brown blood disease.  The nitrite gets into their bloodstreams and makes it impossible for them to breathe.  Their blood turns brown and they die.

High nitrite levels are the inevitable consequence of too high ammonia levels.  The bacteria which make nitrite feed on ammonia to make it. So too much ammonia will mean too much nitrite and goodbye aquaponic system.  This situation is usually caused by overfeeding fish, overstocking fish, or both. This can be further complicated by not having enough plants soaking up nitrate at the hydroponic end of the system-forgetting to plant more seedlings after harvesting crops is a common problem here.

Brown blood disease is usually fatal if allowed to progress. Since you could have 1200 fish in each tank, that is a lot of dead fish to dispose of.

The first way you can tell if you have too much nitrite in your fish tank is that the fish will all be crowding near the surface, desperately trying to breathe. If you see this kind of behaviour, test your water for ammonia, nitrites and nitrates immediately.  Have hundreds of gallons/litres of dechlorinated water ready. Your fish are in the first stages of brown blood disease, most likely, by the time you notice their panic.

If your water tests positive for too much ammonia  and/or nitrite,  you will have to do at least a 50% water change of the whole system immediately, never mind if it is 4 in the morning.  It will be all hands to the buckets and hoses, and the whole change has to be done fast to reduce total ammonia levels in the water in time to save the fish.  This, incidentally, is why it is advisable for the aquaponic farmer to live on the aquaponic farm.  Not so different from farming hogs or chickens, actually. Emergencies always happen in the small hours of the morning when if you are living miles away you will not hear the sensor alarm or be able to get there in time. Losses from brown blood disease are often exacerbated by bad timing and spotty fish tank supervision.

Sensors also break.  The best idea on a substantial aquaponic farm is to have a night shift working on the system who can watch the fish and ammonia levels sensors, if any, and who know what to do if things go wrong in this respect.  Get the dechlorinated water storage tanks going and do that 50% water change! That will be around 4000 litres of water at least that you have to keep aged and dechlorinated in reserve tanks at all times.

The way to prevent this from happening is always to have enough plants growing in the hydroponic section of your aquaponic system, and make sure that the volume of water in your hydroponic section is always at least equivalent to the volume of water in your fish tanks.  The volume of water in the University of the Virgin Islands hydroponic raceways, which are two feet deep, is more than double the volume of water in the fish tanks at any time.

The idea is to get those plant roots soaking up nitrates at a maximum plant root to water volume exposure rate. This will encourage the bacteria to eat more of the ammonia being produced at the fish end.  There are two kinds of nitrifying bacteria, nitrosomas and nitrobacter.  Nitrosomas eats the ammonia and turns it into nitrite. Nitrobacter eats the nitrite and turns it into nitrate. This nitrate is what the plants in your aquaponics eat.  However, if the plants are absent or the bacteria are unhealthy due to not enough oxygen and water flow rate then things get out of whack and you get problems. Every aspect of the system has to be working correctly.  It’s a knock-on effect all around the system that you need to keep going constantly to avoid brown blood disease in aquaponics.

Water pH is very important to keep in balance in order for the nitrifying bacteria to be able to do their job properly. The pH for optimum growth of Nitrosomonas is approximately 7.8 – 8.0. At pH levels below 7.0, Nitrosomonas will grow more slowly, and at a pH of 6.5, Nitrosomonas growth is inhibited. The pH for optimum growth of Nitrobacter is approximately 7.3 – 7.5. Nitrobacter will grow more slowly at the higher pH levels. It is important to note that all nitrification is inhibited if the pH drops to 6.0 or less. At a pH of 6.5, most of the ammonia present in the water will be in the mildly toxic, ionized NH3+ state.  So it is very important to keep your aquaponics water pH at around 7.0 or neutral for this ammonia and nitrites digestion process to get a chance to work.  Otherwise you are risking brown blood disease.

To do this, you will have to test for pH daily and adjust it using calcium hydroxide in tiny quantities  if it goes too low and lemon juice if it goes too high.

You have to add these substances in tiny quantities every couple of hours over days in order not to shock your fish.

In a system of 1000 ltrs (250 gallons) the juice of half a lemon, mixed with a liter of water, would be added initially TO REDUCE PH. Do this gradually in tiny quantities over two hourly intervals. Wait for 24 hours then measure the pH. If a small fall is observed then repeat the process until you have the system down to just below 7.0 in the ideal range as mentioned above.

In a 1000 liter  (250 gallons) system I use one LEVEL tablespoon of hydrated lime (calcium hydroxide, garden lime) CAREFULLY dissolved in 1 liter of water TO INCREASE PH.  Add this gradually in tiny quantities every 2 hours over 24 hours and then test to see how you are doing. USE RUBBER GLOVES WHEN HANDLING THIS. Lime is caustic. DO NOT ADD THIS ALL AT ONCE, ONLY CAUTIOUSLY AND GRADUALLY.

Potassium hydroxide (KOH), old fashioned caustic lye, can also be used TO BRING pH DOWN, ALTERNATED WITH CALCIUM HYDROXIDE and supplies much needed potassium to the system. However, it’s old fashioned lye and it BURNS SO USE RUBBER GLOVES.  For a 1000 liter (250 gallons) system mix a LEVEL tablespoonful of this in a liter of water AND MAKE SURE IT IS PROPERLY DISSOLVED. Add an eggcupful of this mixture (about 1 dessertspoon) every 2 hours and test every 8 hours until you get the correct 7.0 pH reading. DO NOT ADD THIS ALL AT ONCE, ONLY CAUTIOUSLY AND GRADUALLY.  Stop adding it when the pH reads correctly at 7.0.

You also have to make sure that in your solids removal section, the slow mineralization of fine solids in your filter media is going correctly.  Make sure there are no algae hanging around in there, just a moderate amount of fine solids.  Your clarifier should have removed all the gross clumps of fish solids. Also, if solids are allowed to escape and build up in the hydroponic raceways, you can get another secondary nitrification going which will produce more nitrite.  This can get pumped back to the fish and cause that toxic buildup.  So make sure to check and clean out your hydroponic raceways regularly.  Dirty aquaponics will not work.

To avoid brown blood disease, clean out your orchard netting or sponge pad section at least once a week by rinsing the netting or pads out with plenty of dechlorinated water.  Using chlorinated water in your aquaponics will kill the residual nitrifying bacteria who will take at least four weeks to recolonize the netting and pads, during which time your levels of ammonia will remain undigested into nitrites and then nitrates.  Don’t use chlorinated water or water containing chloramine in your aquaponic system if you want stable ammonia digestion by the little bacterial helpers in your solids removal section! Low ammonia levels depend on keeping your nitrifying bacteria in your aquaponics healthy and alive.

Chlorine and chloramine kill nitrifying bacteria. Without enough of both kinds of these bacteria,high ammonia levels will kill your fish, and your plants will not be able to live in an ammonia solution either. Ammonia burns! They need the final product of the work of the nitrifying bacteria, the nitrate fertilizer that has been obtained via the bacteria’s eating the ammonia.  Your bacteria do stage one of the water cleaning process. The plants do stage two.

If the bacteria and the plants are doing their job properly, there will be little risk of brown blood disease in your aquaponics.  If you have low or no levels of nitrifying bacteria in your aquaponics, you risk high ammonia levels. If you have forgotten to balance out your  sysem with enough growing plants, high nitrite and high nitrate levels will occur.  I will deal with the effects of high nitrate levels in another article.

You will need either an ammonia levels testing kit or a dissolved ammonia meter. Nitrite testing and nitrate and nitrite test kits or sensors are also essential to make sure brown blood disease is the problem and not something else.  Nitrite levels should be kept below 4 parts per million. High nitrite levels are toxic.  Ammonia toxicity is one thing, but brown blood disease is caused by excessive nitrite, which can be a companion to excessive undigested by bacteria ammonia.

Levels exceeding 0.55 mg/L (ppm) nitrite-nitrogen can cause brown-blood disease in fish.Ammonia is toxic to fish  even in very low concentrations. When levels reach 0.06 mg/L, fish can suffer gill damage. When levels reach 0.2 mg/L, sensitive fish like trout and salmon begin to die. As levels near 2.0 mg/L, even ammonia-tolerant fish like carp begin to die. Ammonia levels greater than approximately 0.1 mg/L usually indicate that your nitrifying bacteria are in trouble, you have not cleaned out the filtration media such as orchard netting or sponge pads recently, or that the water top-up supply is coming into the system loaded with ammonia, possibly from sewage run-off from cattle or humans.

The danger high ammonia levels pose for fish depends on the water’s temperature and pH, along with the dissolved oxygen and carbon dioxide levels. Remember, the higher the pH and the warmer the temperature, the more toxic the ammonia. Also, high ammonia levels are much more toxic to fish when water contains very little dissolved oxygen and carbon dioxide.  That is another reason to make sure that all your air lines and air pumps are working optimally at all times!

High ammonia levels are also toxic to the plants, don’t forget. It’s the nitrates the plants like, not the undigested fish ammonia.

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′

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