So I'd suggest get the fish first, check his temperament (does he flare often, does he rip apart his food), then try the snail.
I used to have one and he was so cool. He knew the schedule and if you didn't feed him on time
I used to keep one quite happily in a 30 litre tank with a few guppies and a few tetras and a couple of little catfish and a couple of female Betta