Don't believe the 'safe' ranges that some tests suggest.
Ammonia and nitrite are lethal for fish and levels should always be 0. Any detectable ammonia or nitrite indicates a problem.
Nitrate is not so important. The best thing to do with nitrate is to establish what level your tap water contains and try to keep the level in the tank as close as possible to the level from the tap.
is fairly over emphasised by many kits too. The most important thing here is that pH
is stable, not that the number is exactly what you might want. A stable pH
which is too high or too low is far better than making the pH
swing around by trying to adjust it.
Ammonia : Should always be 0. No safe level.
Nitrite : Should always be 0. No safe level.
Nitrate : Keep as close as possible to level in tap water.
: Keep stable rather than worrying about exact value.
Hope that helps you.