As with all things, sometimes they work as planned, sometimes they don't.
I had a Copperband in my system for 3 1/2 years until a couple weeks ago, see pic below.
Prior to getting the CBB, i tried, Pep shrimp, Joe's Juice, Boiling water, Kalk paste and covering them with epoxy, none worked as well as the Butterfly, In my current tank i have zero Aiptasia in the display side, my overflows are full of them, i even used to scrape a few out to feed to my CBB.
In the time i had that fish it NEVER nipped corals, clam mantles or bothered any other fish
They are a delicate fish, maybe i was lucky and found it a very easy fish to care for.
Here's some good info on Aiptasia
Hope this helps