I have had a fluval edge 6.6 gallon aquarium for about three months now. About two months ago I got a blue mystery snail from Petsmart. Up until about 2 days ago he was eating, moving, and acting normally. Then he suddenly died. His shell was growing at a healthy rate and he didn't have any injuries as far as I could tell. I do use a product with a trace of copper in it, but research told me this product was okay. The thing is I wasn't home when he died. I had been gone for about a day and a half with nobody taking care of the aquarium, but the filter, heater and lights were on and the fish could still eat. He died wedged to the bottom with his little trapdoor thing open. Um, once we took his shell out of the water, the part exposed to air turned dark and that's all I can think of. Please help, I want to know what went wrong before I get another snail! R.I.P. my beautiful Omnitron.