Yeah, my black mystery snail (Sabertooth) died yesterday.
What's even worse is that I've only had him for three days!
When I got him at the store he seemed perfectly healthy, slithering up the aquarium wall. But when I put him in my tank after slowly adjusting him to his new environment, he climbed the wall closest to the filter and got caught up in a small whirlpool created by the current. He stayed halfway inside his shell bobbing around for a couple of hours and I tried to submerge him and get him to latch onto a plant or a piece of driftwood, but he would always rise back up to the top. Later on, he came completely out of his shell (well not COMPLETELY, but you know what I mean) briefly for air, sending up his siphon and then retreating back inside his shell, still floating around. That is the most activity I had seen out of him until he died a couple of days later.
I know that mystery snails have both lungs and gills, so it is quite possible that he was just full of air, which would explain the floating and his refusal to sink. What I don't understand is why he kept on floating for two days straight and eventually died. All of my other fish are doing fine and I haven't had any other deaths since setting up the tank, so do snails have special requirements or what?
Maybe snails just aren't my thing, so are there any other algae-eating critters that would fit a 20-gallon tank? I've considered plecos but since they can grow to be six inches long, it would be awfully cruel to keep one in such cramped conditions.
EDIT: The tank is still cycling btw
and the fish are all doing fine even though the ammonia level is rather high (no nitrites or nitrates yet). Are snails especially sensitive to high levels of ammonia in there water, moreso than fish even?