We do not test our tanks, but we are on well water, which has been coming from the same natural source for the entire 30ish years the well has been there, so we know how to manage our tanks and we keep understocked tanks with weekly 50% or better waterchanges. Dino has been keeping fish for about 30 years and I've been keeping them for 2 years, so we have the experience needed (mainly from his 30 years) to handle the tanks in that manner. It is not advised to be done by newcomers to the hobby, but if you aren't going to test the tanks then you need to drastically understock the tanks, use lots of live plants, and do weekly waterchanges (again, we do 50% or better, but never more than 75% for regular changes.)
I agree with Barbrella, that fishstore guy is a newb if he hasn't seen 8.0 pH water in his past. I also agree with Barbrella that the flucuations are worse than the higher pH.
Also, what kind of pleco do you have in that 10g? I ask that because there are VERY few plecos, if any, that would do well in a 10g tank as they get older, especially with other fish in there to increaase the bioload that much more.
