So I had gotten a nerite snail probably at least a month ago, and put him in my 10g shrimp and snail tank. He refuses to stay in the water. I never see him on in the tank, just perpetually surfing the underneath of the lid. I had to get the lid just for him, othewise I'd find him somewhere on the floor after going missing three or four days later. The water is testing fine, the shrimp and other snails are fine, why won't he stay?