Q: Once my aquaponics system is cycled is it going to supply all the nutrients that the plants need?
A: This is a really good question for those out there that are unaware of plant nutrient requirements and how nutrients are supplied to plants in aquaponics. The upfront answer is NO, and here is why. When we're discussing a cycled system what we’re mainly referring to is the nitrogen cycle. A cycled system will provide two key functions in your aquaponics system. The first key function of a cycle system is to supply the macronutrient nitrogen to your plants. Nitrogen is supplied in small amounts through the compound form of ammonium, but primarily through the polyatomic ion nitrate. Nitrogen is needed in the second largest quantity, after carbon, by plants to develop. The second key factor, and just as equally important function of a cycled system in aquaponics, is the removal of toxins; primarily ammonia exerted by fish and produced by decomposing organic material. Ammonia produced from these processes is the energy source utilized to kick start the nitrogen cycle.
The Arrival of Bacteria
Since ammonia is toxic to fish at low levels, there needs to be a process of removing the ammonia out of the system to prevent your fish from dying. Chemoautotrophic bacteria colonize surface areas in your aquaponics system, and they take the ammonia, oxidize it, and use the electrons as a source of energy to build their structures. The oxidation of ammonia changes the chemical composition, which forms another state of nitrogen called nitrite. Nitrite is also super toxic to fish and needs to be removed. Nitrite presence allows other chemoautotrophic bacteria to colonize and oxidize nitrite to produce nitrate. Nitrate is a nearly non-lethal form of nitrogen that plants are able to utilize for growth.
Plants need more Nutrients
This is basically what is going on in a cycle of systems. It’s supplying only one required element that plants need, and also it's creating an environment that is filtering the toxins out of the water. The plant still needs more nutrients to survive, and the rest of the nutrients are going to be supplied via fish food, fish respiration, decomposing organic matter, and adding sources of minerals inside of the aquaponics system.
Brooklyn Saint Mickell