What kind of snails were you looking at getting? I recommend mystery snails. Very interesting snails and fun to watch. They do not eat fish poop. I don't believe any fish eat poop. If you watch them suck some up they will quickly spit it out. There are snails like nerite snails that mainly eat algae. Mystery snails eat algae but you will not even know they are because the tank wont be "cleaned". They mainly eat micro algae. Mystery snails are good scavengers. You do not have to feed them very much because they eat fallen food and the microscopic algae but should be given veggies from time to time. You can feed them lettuce or zuchini etc. I drop in Hikari's sinking wafers for bottom feeders every day and my snail eats the whole thing. Make sure to research the type of snail you want before getting one.
Purple and Red Veiltail Betta - 10 gallon
Blue Crowntail Betta - 2.5 gallon