I'm a little wary of snails. When I was little I had one of those horrid aqua babies kits (guppy, adf, snail, plant, like a quart of water
). The guppy died quickly, poor guy. However the ADF and snail lived quite some time. Then one day I saw some eggs. Then one day they hatched. Then all of a sudden I had like, 40 snails. They ate the plant. Then one day I walked in and saw a giant snail pile on the bottom with a small frog leg sticking out.
So... yeeeeaah... I just don't do snails anymore.
Shrimp are excellent, they're also insanely cute scuttling about the tank and eating everything. They do need hiding places though for when they molt. I bought mine and the night I put them in I had a disaster that forced me to pull them and my fish out and do a massive water change. I think that night they molted due to all of the stress, and Gyarados promptly ate them. Not all bettas snap up molted shrimp, but a lot do so make sure there are small spots under driftwood, rocks and plants they can use to get away from the betta.