After dissolved oxygen, farmers most closely monitor ammonia when raising either fin fish or shrimp when growing in intensive, highly stocked ponds. Ammonia in unionized forms (NH3-N) is the most toxic common pollutant in aquaculture. Even in its less toxic ammonium form (NH4-N), it increases stress on the animals. With increased stress, the shrimp or fish are much more susceptible to disease and have lower feed conversion rates.
When I interact with aquaculture researchers and farmers, I often hear that they need to add ammonia oxidizing bacteria (AOB) to combat high ammonia in the ponds. Multiple companies appear to offer blends of microbes containing AOB – usually NItrosomonas and Nitrobacter sp. For farmers the questions are:
So what alternatives do farmers have for ammonia issues? In my experience ammonia can be combatted best through monitoring and good operations. With low water exchange and high stocking densities, I have found that using a heterotrophic microbial addition can help lower ammonia within 2 – 4 days. In addition to improving waste removal and restoring natural balances, the “cleaner” water now supports better eukaryotic algae growth that efficiently remove nitrogen from the water. Unlike cyanobacteria, the eukaryotic algae cause fewer problems with pH swings and off-flavors.
So unless there are special factors and critical ammonia problems, the addition of true AOB microbes is rarely need in aquaculture. I prefer to see farmers add a balanced blend of probiotic and waste degrading microbes that along with beneficial algae form the majority of waste removal biomass in the pond. For best impact of adding heterotrophic microbes, they should be added early on before the pond becomes unbalanced. With small regular doses throughout the season (with higher does as feeding and animal weights increase), the pond will remain in better ecological balance and animals will experience less stress.
Erik Rumbaugh has been involved in biological waste treatment for over 20 years. He has worked with industrial and municipal wastewater facilities to ensure optimal performance of their treatment systems. He is a founder of Aster Bio (www.asterbio.com) specializing in biological waste treatment.
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