How do I bring nitrite down safely in a shrimp pond?
A nitrite spike is the classic mid-cycle killer in vannamei and monodon ponds. It usually hits between DOC 40 and DOC 70, when feed load overwhelms the nitrifying biofilter. Left untreated for 24 hours you will see brown-tinged gills, surface swimming, and mortality — often mistaken for disease.
Cut feed 30–50% for 48 hours, dose 200–400 kg salt per hectare (or CaCl₂ 15–20 ppm) to reduce nitrite uptake at the gills, run every aerator, and inoculate with fresh nitrifying probiotic. Target NO₂⁻ below 1 mg/L for shrimp, below 0.5 mg/L for fish.
Step-by-step
- 1
Confirm with a fresh test kit
Nitrite kits expire. A false-positive from an old reagent leads to over-treatment. Cross-check with a strip AND a titration kit. Anything above 1 mg/L for shrimp is treatment territory.
- 2
Add chloride to block gill uptake
Nitrite competes with chloride for absorption at the gill. Raising chloride to at least 10–15× nitrite concentration (in mg/L) effectively neutralises toxicity. Common salt (NaCl) at 200–400 kg/ha does this in freshwater ponds; brackish ponds usually already have enough Cl⁻ but check salinity.
- 3
Cut feed 30–50% for 48 hours
Uneaten feed is nitrogen fuel for the spike. Reduce ration, then reintroduce slowly over 3–4 days as nitrite trends down.
- 4
Increase aeration to 100%
Nitrification is oxygen-hungry (4.6 mg O₂ per mg of NH₃ oxidised). Full aeration accelerates biofilter recovery and directly helps stressed shrimp.
- 5
Reseed the nitrifying bacteria
Dose a commercial *Nitrosomonas*/*Nitrobacter* probiotic per label rate. If the biofilter was flushed by heavy exchange or chemical treatment, expect 5–7 days for full recolonisation.
- 6
Partial water exchange as a last resort
10–20% exchange with cleaner source water dilutes nitrite immediately, but throws away the mature bacterial community. Use only if shrimp are actively dying and other steps have failed.
- 7
Log every 6 hours until stable
Nitrite can rebound overnight if feed goes back up too fast. Keep logging every 6 hours for 3 days after the spike, then daily for a week.
When to call a technician
- Nitrite above 5 mg/L with visible mortality — this is an emergency.
- Shrimp gills turn brown or shrimp gather at aerators despite full aeration.
- Nitrite rebounds within 48 hours of treatment — biofilter may be crashed.
- You see cotton-like gill filaments (secondary bacterial infection following nitrite stress).
How CAMARON handles this automatically
CAMARON's water-quality alert engine tracks nitrite trend across your daily logs (and continuously if you have a chemistry probe wired in). The predictive alert fires when the 7-day trend projects nitrite will cross the species-specific stress threshold within 72 hours — usually early enough that a feed cutback alone is all you need.
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