I have a 55g SWFO w/LS no LR. Bak Pak Skimmer, Fluval Canister Filter. My perameters were all PERFECT up until now. I noticed a missing fish. Checked the water, and the ammonia was .5 and the nitrates over 50ppm.:eek: So I did a 30% water change, but the damage was done. I've lost 5 fish...