I've given up on keeping mystery snails in my 5-gallon betta tank - I'm 2 for 2 for them dying within a month.

But I'm still trying to puzzle out why they both died. They followed the same pattern: healthy and vigorous for a week, then mopey for a week, then frequent battened behind the hatch and/or floating, then dead.

The main difference was that Little Ronnie Jeremy, my first snail, was a founding inhabitant of a new tank, so had a diet mainly of blanched veggies.

Cheeto was added when the tank was established and thick with algae, so ate mostly by grazing with occasional veggies.

Just today it struck me that when I set the tank up, I mixed well-rinsed laterite with the gravel. Could that be a culprit? Might there be trace copper in the laterite?