Amaranth pseudograin is the rice of the Aztecs. But it grows much like spinach, and the leaves can be cooked like spinach, too. So you get a green leafy crop with a grain head on top. But it grows like spinach.
The grain amaranth seed head starts as a fluffy purple or orange flower head, that looks like outrageous candy floss. When the grain amaranth seeds ripen, they can be pulled off the flower head with a fork into a container. No further processing apart from sun drying is necessary. The seeds are the product.
Grain amaranth can be cooked like couscous or semolina and is gluten free. It has up to 17% high quality protein content. When the Spanish conquistadores banned it as a devilish crop, people died like flies from malnutrition. The reason the Aztecs worshipped it was because it was a vital protein staple in a world with no real domestic meat animals.
IT GROWS LIKE SPINACH. Grain amaranth likes heat, though. It can grow up to 6 feet tall eventually, so allow for head room. But you would space it like spinach plants in aquaponics.
So you would get the same growth rate in grain amaranth in an aquaponics system as in a spinach plant, I reckon. That is just 30 days from seedling to maturity. Fast for what is essentially a grain crop with a leafy spinach type understory. Two crops in one, and one a staple that can stand in with beans on the side for meat. Of course, your aquaponics system also provides fish. Fish dishes go very well with steamed spinach or grain amaranth leaves.
If you get migraines from spinach, try substituting grain amaranth leaves. Grain amaranth grain is suitable for celiac disease sufferers.
Grain amaranth also provides a lot of grain per hectare even in soil.
You can also sell the flower heads as ornamental flowers. But then you will not get the grain amaranth grain.
I will be planting some grain amaranth in one of my aquaponics systems soon and will be reporting on how it performs.
To find out more about growing food for pleasure and profit in aquaponics systems, I highly recommend reading a few of the following expert books: