Changes

Nitrite is transported across the gills where it enters the bloodstream and oxidises '''haemaglobin to methaemaglobin'''. This leads to tissue hypoxia.

Nitrite is transported across the gills where it enters the bloodstream and oxidises '''haemaglobin to methaemaglobin'''. This leads to tissue hypoxia.

Nitrate toxicity is particularly a problem in '''newly-established recirculating systems''', in which insufficient numbers of bacteria are present in the biological filter. This can also be a problem when the biological filters have been damaged by the interruption of water supply, '''excessive cleaning''' or '''antibacterial administration'''.

Nitrite toxicity is particularly a problem in '''newly-established recirculating systems''', in which insufficient numbers of bacteria are present in the biological filter. This can also be a problem when the biological filters have been damaged by the interruption of water supply, '''excessive cleaning''' or '''antibacterial administration'''.

Species susceptibility to nitrate is '''variable''' and is linked to '''chloride uptake''' by the gills. Nitrite competes for chloride absorption, therefore fish with a high chloride uptake such as the rainbow trout, the perch, the pike and the catfish are more susceptible to nitrite. In contrast, the largemouth and smallmouth bass, bluegill and green sunfish are resistant to high concentrations of nitrite.

Species susceptibility to nitrite is '''variable''' and is linked to '''chloride uptake''' by the gills. Nitrite competes for chloride absorption, therefore fish with a high chloride uptake such as the rainbow trout, the perch, the pike and the catfish are more susceptible to nitrite. In contrast, the largemouth and smallmouth bass, bluegill and green sunfish are resistant to high concentrations of nitrite.

==Clinical Signs==

==Clinical Signs==