How do I lower ammonia in a fish pond?
Ammonia is the invisible killer. Total ammonia nitrogen (TAN) climbs quietly during heavy feeding — and the toxic unionised form (NH₃) doubles for every 0.3 rise in pH. By the time fish are gasping at the surface, gill damage is already done.
Do a 20–30% water exchange, dose beneficial bacteria (Nitrosomonas + Nitrobacter blend), cut feed by 30% for 3 days, and drop pH by 0.5 with agricultural gypsum to shift TAN to the non-toxic ionised form.
Step-by-step
- 1
Test TAN and pH together
TAN alone is meaningless. Toxicity of unionised NH₃ at pH 7.5 vs pH 8.5 differs by 10×. Use a TAN test kit and a calibrated pH meter — both AM and PM.
- 2
Water exchange 20–30%
Drain from the deepest point (highest TAN concentration) and refill from a clean source. Do not exchange more than 30% in one go to avoid osmotic shock.
- 3
Reduce feeding by 30%
Uneaten protein is the primary ammonia source. Feed once a day at 60% of the normal ration for 3–5 days while the biofilter recovers.
- 4
Dose probiotics 5 kg/hectare
Nitrifying bacteria convert NH₃ → NO₂ → NO₃. Apply in the morning with aerators on; expect 48–72 hours for TAN to drop.
- 5
Zeolite 100–200 kg/hectare
Ion-exchange clay that adsorbs ammonium. Broadcast in shallow zones. Not a long-term fix, but buys 5–7 days while probiotics colonise.
- 6
Lower pH with agricultural gypsum
CaSO₄ at 50 kg/hectare drops pH by 0.3–0.5. This shifts NH₃ ↔ NH₄⁺ equilibrium toward the non-toxic ammonium form without adding to the ammonia load.
When to call a technician
- Fish gasping at the surface with red or frayed gills.
- TAN above 2 mg/L or unionised NH₃ above 0.1 mg/L after 48 hours of intervention.
- Mortality spike coinciding with a pH swing above 8.8.
- Green-to-brown pond colour flip (algal die-off releases stored nitrogen).
How CAMARON handles this automatically
CAMARON's water quality module tracks TAN, pH and temperature together and computes unionised NH₃ in real time using species- and life-stage-specific thresholds. Alerts fire when the toxic fraction crosses 0.05 mg/L — hours before visible gasping.
Start free