Sources
In aquaria and ponds nitrites are produced by Nitrosomonas
bacteria when ammonia is broken down.
Measurement of nitrite
Test kits are available (some of these measure Nitrite-Nitrogen,
a conversion factor being applied to the result to obtain
a true Nitrite reading: full instructions should be available
with the test kit used.
Safe levels of nitrite
In its "Water Quality Criteria", OATA recommends that Nitrite
should not exceed 0.2mg/l in freshwater and 0.125mg/l in seawater.
Nitrite poisions the fish by binding to the haemoglobin in
the blood preventing it carrying oxygen, in effect suffocating
the fish. The gills of fish dying as a result of nitrite poisoning
are a characteristic brown colour.
In freshwater the toxicity of nitrite may be reduced by the
addition of small amounts of certain salts. Proprietary products
for these purposes are available.
Reduction of high levels of nitrite
Levels can be reduced by any, or a combination of the following:
- general husbandry, stocking and feeding improvement procedures
- improvement of biological filtration
- dilution by water change
