Nitrite / Nitrates

Nitrites may build up to levels where fish kills may occur. Optimum levels of nitrite is less than
These bacteria are utilised in the biological filters that are used to decrease the level of ammonia and nitrite in the water and are also present in the substrate of ponds and dams. The process is called

Telltale signs of nitrite poisoning
Nitrite poisoning is often termed "brown blood disease" as it causes the gills to take on a tan/brown colouration.
Examining the gills can determine if nitrite is the cause of the problem.
Nitrite in the blood changes the haemoglobin, which transports oxygen to methemoglobin, which does not transport oxygen. This results in respiratory distress and ultimately death.

Controlling the problem

Both ammonia and nitrite levels can be controlled by:
  • performing partial water exchanges within the system (i.e. flow),
  • reducing the amount of food given
  • reducing the stocking density in the system

Generally Nitrates should not pose a threat to your system - the level of nitrates is best controlled by the addition of grow beds - it is important that you have sufficient grow beds to match your stocking density