The waste creates issues with ammonia/nitrite, cyanobacteria blooms, and buildup of anaerobic sludge layer on the pond bottom. Additionally, the high stress caused by pollution often allows for growth of opportunistic pathogenic microbes.
The earliest solution was to flush the ponds with new water, however downstream pollution and costs associated with water changes led farmers to see if the principals of biological water treatment could be used to improve animal health and lower costs.
Aquaculture products work in three distinct ways (some organisms function in more than one manner).
- Bioremediaton - added cultures degrade organics, remove ammonia/nitrite, and help reduce sludge buildup on the pond bottom. By reducing pollution, the cultures also reduce animal stress.
- Biocontrol - the cultures work via competitive exclusion to reduce the density of opportunistic pathogens. Frequently, bioremediation cultures also have biocontrol capabilities. For example, Bacillus subtilis exhibits antagonistic properties to Vibrio sp and several problem cyanobacteria species.
- Probiotic - while fish consume all the added microbes (they live in the water), some microbes are able to reproduce in the digestive tract which helps improve feed conversion rate. In addition, probiotics often help stimulate an improved immune response to challenge by pathogens.