Analysis of Excessive Ammonia Nitrogen in Pond Water for Aquaculture Fish, Shrimp and Crabs

[Cause Analysis]

• During aquaculture, the problem of excessive ammonia nitrogen in ponds is frequently encountered. Excessive ammonia nitrogen can lead to reduced immunity and resistance, decreased feeding, slow growth and susceptibility to disease in farmed fish and shrimp.

There are three main sources of ammonia nitrogen in ponds: produced by the decomposition of fish feces, fertilizers, residual bait and dead animals and plants; produced by nitrite and nitrate under the action of denitrifying bacteria when dissolved oxygen is insufficient; produced by metabolism within the bodies of fish and shrimp and released into the water through gills, urine, etc.

1. Ponds with duck sheds, pig pens, etc. beside them, where large amounts of manure are directly discharged into the pond every day;

2. Ponds where excessive use of strong chlorine, bleaching powder, copper sulfate, etc. causes massive death of phytoplankton (i.e. algae crash). Algae crashes are more common from May to September, and the risk in July and August is higher than in other months. With high fish density and high temperature, especially in August, when the temperature turns from high to low, the upper and lower water layers convect, easily stirring up the bottom, leading to oxygen deficiency and pond turnover;

3. Ponds where large amounts of feed are given, but the fish do not feed actively;

4. Ponds with excessive zooplankton such as copepods, cladocerans and rotifers;

5. Ponds where sludge is not cleared for a long time, no microecological preparations are used, and the substrate is not improved.

[Solution] How to prevent excessive ammonia nitrogen?

1. Ferment farmyard manure before putting it into the pond. Fermented farmyard manure consumes less oxygen than unfermented manure and is more easily absorbed by algae;

2. Strong chlorine, bleaching powder, copper sulfate, etc. are "medicine" when used well and "poison" when used poorly. Use them with caution!

3. Carefully observe the feeding situation of the fish, and adjust the feeding amount at all times according to how they eat;

4. Kill off excess zooplankton in a timely manner;

5. Regularly clear sludge, use EM bacteria and black bottom-improving agents. Among these, microecological preparations have better effects, but they need to be used consistently and over the long term.

[Further Reading] So how do you control ammonia nitrogen in water bodies?

1. After the farming period ends, clear sludge and dry the pond, and use quicklime, strong chlorine, bleaching powder, etc. to disinfect the pond bottom and remove ammonia nitrogen.

2. Changing the water is the fastest and most effective way. The new water added must be of good quality, and the temperature, salinity, etc. of the new water should be as close as possible to those of the original pond water.

3. Cultivate good algae in the pond, use aerators, bottom oxygenators, etc. to maintain sufficient dissolved oxygen, speed up nitrification, and reduce the concentration of ammonia nitrogen.

4. Use high-quality feed, reduce the feed conversion ratio, avoid overfeeding, reduce residual bait, and reduce ammonia nitrogen emissions.

5. During the farming process, regularly use ammonia-nitrite rapid purifier, photosynthetic bacteria, EM bacteria and other microecological preparations to oxidize harmful ammonia nitrogen into nitrate that algae can absorb and use.

6. Other measures: including reasonable stocking density, regular testing of water quality indicators, controlling water pH between 7.6-8.5, and avoiding excessively high pond pH, etc.