Poor water quality

What is it?
Poor water quality is a term used to indicate that the aquarium tank water is not of optimum quality for the animals or plants in the tank.

Generally the aquarist needs to ensure the water has the ideal ingredients dissolved in it for the benefit of the lifeforms living in it and none of the chemicals which may be toxic to them.

The chemicals generally associated as being unwanted are primarily:


 * Ammonia


 * Nitrite


 * Nitrate

But other undesirable items are:


 * Phosphate (generally wanted at some level for planted tanks)
 * Carbon dioxide (generally wanted at some level for planted tanks)
 * Metals (low levels are essential for life. But high levels are toxic)
 * Dissolved organic material, see redox level.