Symptoms
Red or bloody streaks along gill covers and fin edges — this is chemical burning.
Gasping at the surface, lethargy, clamped fins, refusal to eat. Severe cases: fish lies on the bottom barely moving.
Emergency Action
Immediate 50% water change with dechlorinated water matched to tank temperature. Use Seachem Prime at 2× dose — it binds ammonia for 48 hours.
Test ammonia immediately. If above 1 ppm, repeat 50% water change every 2-3 hours until below 0.25 ppm.
Recovery Care
Keep water pristine for 2 weeks. Daily small water changes. Feed lightly — damaged gills need recovery time.
Add aquarium salt (1 tsp per gallon) to help fish produce slime coat and protect damaged tissue.
Prevention
Cycle the tank before adding fish. Test ammonia weekly with a liquid kit.
Never skip water changes. Overstocking and overfeeding both spike ammonia.