The role of nitrogen in any living organism is vital, so it comes as no surprise that nitrogen in aquaponics systems needs to be discussed and understood. In a recent video and blog post, Bright Agrotech outlines the sources and ways in which nitrogen in aquaponics systems performs major roles. The main compound is nitrate, but it is only the final end product of the reduction of ammonia to nitrite to nitrate.
The blog post Nitrogen in Aquaponics is even more complete in delving into the role of nitrogen in aquaponics:
Nitrogen typically occurs in several forms in the natural world. Nitrogen is used to make amino acids, which are used to make protein. All plants and animals contain proteins, and when they die, other organisms consume them and scavenge these proteins for energy and parts.
When land animals consume proteins they eventually break them down into amino acids and then to ammonia. Ammonia (NH3), is very nasty stuff- it’s very toxic, and the best way to get rid of excess ammonia is to excrete it. In order to make it safe until it can be excreted, in land animals, ammonia is converted to chemical called urea and excreted in urine.
In fish it is much simpler. Ammonia is usually present as Ammonium (NH4+) which moves across the cell membranes of the fish and eventually diffuses out into the water. Depending on the pH, ammonium may mostly stay ammonium or turn into ammonia, which can be very dangerous. Ammonia has no charge, so the fish have difficulty keeping it out of their bodies. Uncharged, the ammonia molecules can seep back into the fish’s cells and poison the fish.
Nitrogen in Aquaponics needs to be made safe as Nitrate
Ammonia can be very toxic, but if the pH is kept at levels Dr. Storey recommend, 6.0 – 6.4, the chances of it being deadly are greatly reduced since it is mainly ammonium. However once ammonium is reduced to nitrate, there is no safe buffer. It needs to be oxidized into nitrate which is again much less toxic to the system but still needs to be removed. That is where the nitrogen in aquaponics is removed by the plant level.