Hi. Firstly a quick intro and a thank you... 1) Intro: I am finally near the end of my cylcle (prolonged by the usual newbie ignorance - I over cleaned the filter and started using chemicals instead of regular 50% water changes etc) 2) Thank you: This forum has been the knowledge bank that has prevented the death of the fish is my son's (yes, I know) over stocked tank (which will be resolved upon house move after Christmas, until when I will make as many water changes as needed). Unlike other forums I discovered when looking for help, this site has provided constructive, understanding advice, rather than the critical and sometimes almost nasty remarks on others. 3) My position: I am now 'getting there'. Ammonia is almost 0 and I am doing almost 50% water canges twice a day to dilute the Nitrite levels which are 1.0 before each water change. At the same time, Nitrate has now risen from 0 to 40, which I know is all part of the cycling and an OK level for the fish I have, but I am concerned that it is going to rise (I read likely to be caused by overstocking/overfeeding- ie, I assume, too much Ammonia), which I will not be able to help with water changes as my tap water is also reading 40. 4) What I don't understand: If the Nitrate of my tap water has been 40 all along, how did it get REDUCED to 0 throughout cycling when Ammonia levels were high? And now knowing that water changes are not going to help if the Nitrates do rise too high, is there anything elsae that I can do (I have TeraAqua NitrateMinus, but am lead to be sceptical with regards the effect of such chemicals) Sorry that it's a long one, but have tried to explain my specific query, which I couldn't find answered elsewhere.