I do a 20% PWC once a week. the only thing I have a problem with is the Ph. it drops to about 6.0 other than that everything has always been great. same ph issue in my 6g. I have ample filtration on both tanks. and I do agree on the over stocking. I plan to set up my 60g soon. but I'm hopefully moving. so I wanna wait. I keep my temps at 80f. I was told. that at that temp they would be brighter. more active. but live a shorter life. could this be the problem.? is he expiring.? every one else in the tank looks happy and busy.