Are there any fish that will eat snails and are okay as a lone specimine?

Some kind of puffer?

Pea puffers. They will be happy with, they say, 5 gallons for the first, 3 for each after, so 3 is tight in a 10 gallon. 20 gallon is best and can have 4 or 5. best to get fewer males which have a darke stripe down the middle of their stomach. smaller less dominate males can try and hide as a female with a lightened stripe. They'll eat a bunch of snails tho, a few each day per fish. I would recommend 3 puffers in a heavily, heavily planted 10g for the very smallest possible. That's what my 3 are in. And I have more tanks with a bunch of snails that I pull from. Bloodworms are mostly all they eat (other than snails of course) if I don't starve them a bit first.

Pea puffer is a great suggestion.

I guess what would be best would be to tell us about your tank...its parameters...size...current inhabitants and then it would be easier to recommend a fish for you!

pea puffers are rlly cute and they will fit

also make sure to actually feed them other foods and i heard they like a lot of plants too