The Yellow Pyramid Butterfly (Hemitaurichthys polylepis) and Zoster Butterfly (Hemitaurichthys zoster)are planktivores (eat out of the water column) and considered reef safe. They're out of stock on Live Aquaria, but you can do a search for them to check out their descriptions. I have the yellow pyramid in QT right now, so I haven't had a chance to observe it with corals.