Welcome to the forum!
Be aware that snails do poop a lot, so you may need to clean your tank more often. Theyre even messier than fish.
They also, IME, need to be removed from the tank to eat because your betta will try to eat their food >.<
I dont know anything about guppies or small fish like that.
You could also try ghost shrimp, but theres a chance he will eat them. Some bettas eat them, some dont.
“Some people talk to animals. Not many listen though. That's the problem.”
― A.A. Milne
Espeon female halfmoon / 10G
Jolteon male dumbo plakat / 10G