Thanks mate, did about 40% change lastnight will test again when I finish workSeems like you're going to need another change to decrease nitrate (at some point = only since its increasing quickly). Remember if you change 50% the nitrate will drop to 20-40 - assuming that no new nitrate is being produced. I would completely ignore nitrite readings. Remember also that between certain tests, nitrate and nitrite can interfere - and results in false positives. You can certainly do a water change - but until your ammonia is lower, you are probably causing some fish damage - assuming the test is correct. Ammonia also feeds algae.