Hello everyone! Thanks Mike for welcoming me this morning. I have a few questions which have been bugging me. My tank (20 gal) has been set up now for approximately 6 weeks and I've since learned that the tap water here is very, very hard; so, with each water change (began last week), I'm using RO water. I did a fishes cycle before adding my first fish and currently I have 4 fish in the tank. My question is: Is it necessary to test the water BEFORE AND AFTER a partial water change? Testing the water before doesn't seam to make sense to me as the water chemistry will change with the water change anyway, so to me that is a waste of testing solutions. I'll be doing my next weekly water change this coming Monday (6-13), so some feedback before then is much appreciated! Also, is it still necessary (with RO water), to add, say, PRIME or STABILITY, for example, with each change (I know I don't have to worry about the chlorine. Finally, I'm having to re-establish my 'hospital/ quarantine tank' - tear it down and start over with RO water. Is it necessary to add good bacteria starter to that as well? ThankX! That should be 'fishless cycle'. This auto correct gets me some times!