Yoyo loaches are very good snail eaters. When I had them they didn't bother the other fish at all. I suspect they would eat all snails in the tank, including assassin snails. I believe they also eat baby shrimp, but I'm not real sure about that. The don't bother plants at all. Another beautiful loach is the "Zebra loach", Botia striata, which is a little smaller, and, in my experience, less intent on staying hidden.