I won't be putting any fish in this one, a 3.7g is too small for anything to live in (the livable space isn't even a full 3.7g either, since there's a compartment blocking off the filter). I toyed with the idea of it being an emergency quarantine tank in case a fish did get sick, but at one point the betta living in there had some tiny outer parasites so it's probably unsafe to reuse this tank. The parasites didn't seem to bother shrimp or snails, so I could probably just stick with them.
Mainly I just want to make sure the tank will remain cycled for the snail itself, so that she's healthy and safe. I have been considering possibly adding 5-10 cherry shrimp to it later.