They are good for keeping your snail level down. My clown loach isn't aggressive at all IMO, but others may say different. IMO, I think that yo-yo loaches are better for keeping down snails and you can have more in a tank.
They do really well in a community tank. The big problem with Clown Loaches is that they get really big and need lots of room and extremely clean water. They are more prone than other loaches to ICH. Theyare great snail eaters and may knock a plant over now and again trying to get at one but they don't eat plants. Now on the upside - they have enormous personalities. Mine eat from my hands and recognize me when I come into the room (They beg for food) When my husband comes into the room they may check him out but they don't beg He calls them puppies because thats how they act.