The last surviver of the baby snails i got from petsmart appeared to be dead.ive had him for 8 months now and hes more then doubled in size sense i got him. his shell is now about half a cm in diameter. I found him laying on the bottom of the tank in a spot where one of my fish moved the marbles so he was just laying on the glass. his shell was on its side and he was mostly out of his shell. i hoped he would move but he stayed there without moving for 2 days out of his shell and all. the third day i was going to remove him from the tank and he was gone. i thought another fish ate him, but a couple hours later i saw him climbing up the side of the tank. im now afrade that he will really die. i think he may be sick. his shell is still transparent. is this normal for how big he is? is there anything i can do for him? and i still cant explain his strange behavior.