I lost my golden mystery snail a few weeks back, now it looks like my blue mystery is gone too. The only thing off on my parameters is the PH. Its at 8.2
Doubt any fish are doing it I got a pair of angels, a school of Cory cats,a school of glow fish tetras, and a school of red rainbow fishInverts like mystery snails are highly sensitive to copper and will be killed by levels that are harmless to other fish.
Another thought: Could a fish be killing them?
My snail keeps me guessing daily where he is and what he's doing. This morning I got up, certain he was dead because he was sucked onto the intake for the AquaClear. I turned off the power, tapped his shell lightly with a net, and he disappeared back into his shell and fell to the bottom. Little nuisance is doing great.My blue mystery is fine now he's back on the glass munching away on the algae.
I keep cuttlebone scattered around the tank for them to stop by for a calcium snack when they feel like it.