An interesting aspect of aquaponic culture is how such a small population of fish can provide the nutrients for a sizeable number of plants. Also interesting is the fact that the fish supply all the nutrients required. Nothing else needs to be added. The nutrients come from the decomposing fish wastes. Nitrogen, for example, is produced when the microbes decompose the manure. The material is first converted into ammonia and then into a form of nitrogen usable by the plants. This decomposition also takes place with other manures such as cow manure but the resulting organic fertilizer is not considered a complete nutrient source. Other nutrients are usually added. Why are they different?
One explanation that is fairly well accepted is that the diverse microbial life in an aquatic environment produces the needed nutrients from the available organic matter. This makes sense since many different microorganisms thrive in a watery environment. In that environment there are fish providing manure and there are plants and their roots to which the microbes can attach and maintain their symbiotic relationship with the plants.
The rapid growth of plants in an aquatic environment populated by fish has not gone unnoticed. The process may not be fully understood but it is obvious that nutrients are being efficiently produced by the microbes decomposing the organic matter and interacting with the plant roots to provide the nutrients to the plants. A thriving aquaponic supply industry has developed as well a many aquaponic growers and enthusiasts. Not everyone is able or has the inclination to set up the infrastructure to raise fish and plants in the same environment. The knowledge learned from these processes can be beneficial in advancing organic gardening and farming. How that advancement can be done might be the following:
- Promote the use of organic products from an aquatic source. Sea weed,kelp, fish meal, fish manure.
- Promote the capture of more fish manure from commercial production facilities.
- Promote those products that maintain the live aquatic microbial life. Some products such a fish entrails and dead fish may be pre-processed to the point where none of this microbial life remains.
- Promote the use of humus compost where fish manure is composted with some clay to bind the carbon and provide a moist environment to maintain the microbial life.
When making compost tea from composted cow manure some aquatic based substance is often added to improve the microbial life in the compost tea. Aquatic substances such as seaweed and kelp are easily obtained but fish manure is not. The manure from fish in the ocean or in ponds is diffused and widely distributed in the water. Sifting it out is not practical. The only practical method of collecting fish manure is when they are grown in enclosed facilities such as aquariums, continuously re-circulating systems or raceways.
Unfortunately much of this filtered waste is not collected for any commercial purpose and ends up in some sewer system. A waste of extremely valuable material.
Some hatcheries and re-circulating fish production systems have been fined for discharging unprocessed wastes into rivers and streams. To prevent these fines and to comply with environmental restrictions they pay to have the wastes hauled away and disposed where there is no environmental damage. These wastes can be processed on site to create a valuable source of organic nutrients and microbial life for all types of agriculture.