When Ammonia Rises — Five Things to Do, in Order

The most common mistake when ammonia exceeds its threshold is skipping steps — exchanging water before identifying the source, or dosing probiotics and waiting. Work through the following in order. ■ First understand this — pH decides ammonia toxicity Your test kit usually reports total ammonia nitrogen (TAN). Only the un-ionized fraction (NH₃) is actually toxic to shrimp, and that fraction depends heavily on pH. At the same total ammonia concentration, the toxic fraction is about 1.2% at pH 7.5 but rises to roughly 11% at pH 8.5 — nearly tenfold. So an ammonia number alone means nothing; you must read it with pH. The same 1 mg/L is comfortable in a pond at pH 7.5 and an emergency in a pond at pH 8.7. ■ Step 1 — Cut or stop feeding immediately Ammonia comes mostly from uneaten feed and waste. Taking other measures without cutting the source is like bailing water with the tap still running. Stop feeding, or halve it, for at least a day — up to two if the reading is high. Shrimp survive several days without feed. ■ Step 2 — Check pH and bring it down if you can If pH is above 8.5, that is now your most urgent problem. Manage CO₂ through aeration and stop any liming immediately. Bringing pH down to around 8.0 alone cuts actual toxicity by more than half. That said, sharp pH swings are themselves dangerous — never force a change greater than 0.3 in a day. ■ Step 3 — Push oxygen to maximum Shrimp exposed to ammonia have damaged gills and reduced oxygen uptake. A DO level that would normally be fine is not enough now. Run aerators at full. Oxygen is also required for nitrifying bacteria to break the ammonia down. ■ Step 4 — Water exchange comes after that Only now consider exchanging water. Never change more than 30% at once; do it in 20–30% portions. Always measure the incoming water's temperature, salinity and pH first and compare with the pond. Losing molting shrimp to a sudden salinity shift while chasing an ammonia number is a frequent accident. ■ Step 5 — Probiotics are prevention, not emergency medicine Nitrifying bacteria take days to weeks to establish. This is not a product you dose today to lower today's reading. Probiotics work when applied routinely — especially when starting a new pond and right after disinfection — not after the incident. ■ Afterwards, always watch nitrite Ammonia breaks down into nitrite. It is normal for nitrite to rise a few days after ammonia falls. Relaxing at this point invites a second incident. Check nitrite daily for a week after any ammonia event. Shrimp365 records ammonia together with pH so you can judge real toxicity risk rather than a bare number.