The Hazards of Nitrite in Aquaculture and Corresponding Solutions

2026-06-05

I. Causes of Formation

Nitrite is an intermediate product in the conversion of ammonia to nitrate. During the mid- and late stages of aquaculture, extensive feeding leads to the accumulation of uneaten feed and excreta in the water. Coupled with the regular use of disinfectants, this disrupts the microbial balance, resulting in insufficient oxygen supply. Consequently, the nitrification process that converts accumulated nitrogen compounds is impeded, causing elevated levels of ammonia‑nitrogen and nitrite in the culture water. However, because ammonia‑nitrogen is converted relatively rapidly, nitrite becomes the most pressing issue.

II. Causing Harm

Nitrite can enter the bloodstream through the gill filaments, impairing the blood’s oxygen‑carrying capacity and leading to tissue hypoxia. At this stage, fish and shrimp exhibit reduced feed intake, develop pathological changes in the gill tissue, and experience difficulty breathing and restlessness. In severe cases, nitrite poisoning may disrupt the function of key metabolic organs, resulting in physical debilitation; under such conditions, fish and shrimp become highly susceptible to disease and mortality.

III. Solutions

1. On sunny days at noon, operate the aerator more frequently to break up water stratification, promote photosynthesis by algae in the water column, and ensure adequate dissolved oxygen levels, thereby facilitating the conversion of nitrite to nitrate.

2. Regularly apply Di Gai Bawang for bottom-conditioning and Bi Shui Jie Du An to detoxify the pond. This helps reduce oxygen consumption at the pond bottom while minimizing the adverse effects of nitrite on fish and shrimp.

3. Use a probiotic microbial consortium combined with phosphate fertilizer (to balance the nitrogen-to-phosphorus ratio in the water) and Diatom Wang to condition the water and enhance oxygen production by pond algae.

Real-world case studies

Date: July 20, 2024

Location: Xintan Salt Farm, Yancheng, Jiangsu Province

Cultured species: Common carp intercropped with whiteleg shrimp

Cultivation area: 200 mu, with a water depth of 1.6 meters.

Water parameters: Ammonia nitrogen 0, nitrite 0.6, pH 8.0

Situation description: Affected by the plum rain season, several consecutive days of overcast and rainy weather have caused the pond water to become turbid and depleted of nutrients. Shrimp exhibit surface‑floating behavior in the early morning, while carp have noticeably reduced feed intake. Measurements indicate that nitrite levels have risen to 0.6 mg/L; a preliminary diagnosis suggests that post‑rain water depletion, combined with elevated nitrite concentrations, has triggered oxygen‑depletion stress in fish and shrimp.

Handling Plan

  1. On the first morning, apply Bishui Jiedu’an (40 mu per bottle) for detoxification and Di Gai Bawang (100 mu per bucket) to improve the pond bottom; in the late evening, soak probiotic pellets and Diatom Wang as a reserve.

The next day, first apply the soaked probiotic pellets and diatomaceous earth‑enriched fertilizer water, then use phosphate fertilizer to maintain a balanced nitrogen‑to‑phosphorus ratio in the water, thereby promoting nutrient‑rich conditions.

On the third day, apply Super Gold Bacteria by spraying (40 mu per box) and spread Oxygen‑Boosting & Detoxifying Bottom‑Improving Agent dry (50 mu per bag) to improve the pond bottom.

Processing Result

Two days after applying the fertilizer, the pond water changed from turbid to a tender green hue; in the mornings, the phenomenon of fish and shrimp surfacing for air disappeared, and the carp’s feed intake improved markedly. Measurements showed that the nitrite level dropped from 0.6 to 0.2, while the pH rose to 8.6. Four days later, the nitrite level had further declined to 0.05.

Case Analysis

In the mid-to-late stages of freshwater fish farming, feed input increases significantly, leading to the accumulation of feces and uneaten feed, which in turn raises oxygen consumption at the pond bottom. Coupled with cloudy, rainy weather that reduces water fertility, insufficient bottom‑level oxygen can cause elevated levels of nitrite, adversely affecting the normal growth of fish and shrimp. Bishui Detox An can directly reduce the toxicity of ammonia nitrogen and nitrite in the water, break down water stratification, and enhance the transfer of atmospheric dissolved oxygen into the water. The probiotic complex contains multiple beneficial active strains that not only absorb and convert ammonia nitrogen and nitrite but also promote algal growth. Applying phosphate fertilizer helps balance the nitrogen‑to‑phosphorus ratio in the water, preventing nitrogen overload. When the water is too clear and nutrient‑poor, Diatom Wang can be used to rapidly enrich the water, providing the pond with adequate nutrients.

The dissolved oxygen in the soil, combined with probiotic consortia, can make fertilizer efficacy last longer.

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