I'm sorry I couldn't remember what you have in that tank.... Is it just the 3 ADFs? If yes is the answer, I would think you could get away with 5 in a 10G tank. My LFS counts ADFs as 2 cubic inches. Or maybe do 4 and an oto for cleaning.
I'd like to know what you end up doing (and of course see pictures!) Keep posting!
I know our great LFS has snail in with their ADFs. I have read on this site that snails can multiply on you, so you might want to start low and see what happens. I wish I could help more....
I really am interested in what ends up working for you and what you add to the tank, so let me know.