Second on the trumpet snails - although if you are aquascaping and trying to keep different shapes in your substrate they are a bad idea because they will dig until it's leveled out again xD!!
If they get out of hand - get a clown loach - they love them - the pea puffers will bite at them as well but their favorites are the Physa snails (which are harmless to any plants that I've had and lay those clear jelly egg sacs which some fish enjoy eating!)
They are also easy to breed - along with the trumpet snails - in fact, you can't help it, lol. My puffs did run out of Phsya snails and I had to buy some locally and breed some myself in a little snail jail