I have a 10 gallon long time cycled tank that I use for my Male Betta. I thought he might like some company (actually my son did) so we added a Mystery Snail. In short, the snail died. Tried another, and he died too. Both were acclimated properly and there is no salt or medications in the water. Not wanting to kill another, my question is what else might I keep with the Betta?