I've had my rabbit snail in my 29 gallon for over 1.5 months now. He was always really active and moving around my tank looking for food. 4 days ago he didn't come out of his shell the whole day. For the next 3 days he was tucked really far up inside his shell and in the same spot of my tank. I picked him up today and smelled his shell to see if it smelled rotten but it didn't. I know he's not dead but how long can he go without food and without coming out of his shell? I'm really worried about him. My water parameters are 0 ammonia, 0 nitrite, 7 nitrate.