Hi,normally I keep my tank at 76-78 degrees, but with no A/C in the house it gets up to 80-83.5 from room temp. and my heater stays unplugged. we have hard water here in the high desert and my PH is 7.2 I have a Magnum 350 deluxe canister filter and on the opposite side of the tank, i have a powerhead attached to a sponge filter. I have never had a problem with fish loss until the guppies. In fact, when i restarted my tank 4 years ago when we moved to Nevada, i used 20 tetras ( some call them berry tetras & some say skirt tetras ) as my start up fish to recycle the tank. all of those fish survived and 4 years later, i still have 11 of them. I will post a link to pictures of my tank further down in the thread. meanwhile, here is a good article on fish acclimation. http://www.liveaquaria.com/general/general.cfm?general_pagesid=19&ref=3319&subref=AI