Have had no problems with ours. In with an orbic cardinal and an orange-spotted goby. He's low man on the totem pole, though I did watch him tease the other 2 repeatedly tonight (swim by close & flare fins, no reaction so he gave up). Definitely a jumper, he hits the lights almost every day for no reason.
Ate all of the pyramellid snails (which is why we got him), but he hasn't touched the small strombus snails, the stomatellas, or the ceriths. He might be keeping the red planaria in control, or they may just be keeping their own population in control, not sure on that as I've only seen him go after them after cleaning the glass or blowing them off a rock.
I've never seen any collonistas in this tank, so can't comment there. We have one small peppermint shrimp and one small candy cane pistol & he ignores them both. The only annoying thing is he'll pull the mysis out of the palys and LPS, then spit it out & not eat it LOL.