Symptoms of Brown Blood Disease
Nitrite binds with hemoglobin, forming methemoglobin — fish blood literally turns brown. Symptoms: rapid gilling, gasping at surface, dark gill color.
Fish suffocate even with normal oxygen levels. Same symptoms as ammonia poisoning, often confused.
Salt Therapy (Critical)
Sodium chloride blocks nitrite uptake by gills. Dose 1 teaspoon per 5 gallons immediately upon detecting nitrite spike.
Plain salt (no iodine) only. Marine salt is fine. Continue salt until nitrite reads 0 for 7 days.
- ✦Skip salt for scaleless catfish, tetras, and African cichlids that prefer hard water already
- ✦Increase aeration during nitrite spike — gives fish oxygen reserves
- ✦Do small daily water changes (10-15%), not one big one
Why It Happens Mid-Cycle
Ammonia-eating bacteria multiply faster than nitrite-eating bacteria. So in week 2-3 of cycling, ammonia drops to 0 but nitrite spikes high.
This is normal. Stay patient — nitrite-eating bacteria will catch up within 5-10 days.
After Recovery
Test for 14 days continuously after the spike. Sometimes nitrite returns when bacteria die back from medication or temperature shocks.
Slowly reduce salt over a week of water changes if you used salt therapy.