Nitrite Poisoning
Disease Type: Environmental
Cause: Nitrite
Names: Brown Blood Disease, Nitrite Poisoning
Description: Nitrite poisoning follows closely on the heels of ammonia as a major killer of aquarium fish. Just when you think you are home free after losing half your fish to ammonia poisoning, the nitrites rise and put your fish at risk again. Anytime ammonia levels are elevated, elevated nitrites will soon follow. To avoid nitrite poisoning, test when settng up a new tank, when adding new fish to established an tank, when the filter fails due to power or mechanical failure, and when medicating sick fish.
Symptoms:
Fish gasp for breath at the water surface
Fish hang near water outlets
Fish is listless
Tan or brown gills
Rapid gill movement
Also known as 'brown blood disease' because the blood turns brown from a increase of methemoglobin. However, methemoglobin causes a more serious problem than changing the color of the blood. It renders the blood unable to carry oxygen, and the fish can literally suffocate even though there is ample oxygen present in the water.
Different species of fish tolerate differing levels of nitrite. Some fish may simply be listless, while others may die suddenly with no obvious signs of illness. Common symptoms include gasping at the surface of the water, hanging near water outlets, rapid gill movement, and a change in gill color from tan to dark brown.
Fish that are exposed to even low levels of nitrite for long periods of time suffer damage to their immune system and are prone to secondary diseases, such as ich, fin rot, and bacterial infections. As methemoglobin levels increase damage occurs to the liver, gills and blood cells. If untreated, affected fish eventually die from lack of oxygen, and/or secondary diseases.
Treatment:
Large water change
Add salt, preferably chlorine salt
Reduce feeding
Increase aeration
The addition of one half ounce of salt per gallon of water will prevent methemoglobin from building up. Chlorine salt is preferable, however any aquarium salt is better than no salt at all. Aeration should be increased to provide ample oxygen saturation in the water. Feedings should be reduced and no new fish should be added until the tank until the ammonia and nitrite levels have fallen to zero.
Nitrite is letal at much lower levels than ammonia. Therefore it is critical to continue daily testing and treatment until the nitrite falls to zero.
