Health guide, not a diagnosis · Serious
Nitrite poisoning (brown blood)
Also called brown blood disease, nitrite
Signs
- Gasping at the surface
- Brown or dark gills
- Many fish sick at once, often in a new tank
Cause
Nitrite from an uncycled or overloaded filter stops the blood carrying oxygen.
What to do
Test for nitrite. Do a 50% water change, add water conditioner and a small amount of aquarium salt (the chloride blocks nitrite), add aeration and feed less until nitrite is zero.
If a fish is badly ill, talk to an aquatic vet.
Prevention
Cycle new tanks; add fish slowly; don’t overfeed.
Medicines used for it
Always read the label first
Species often affected
0 species