Goatfish

Two species in three tiers each: the Yellow Goatfish and the Bicolor Goatfish (Parupeneus barberinoides). Goatfish hunt with a pair of chin barbels, probing sand for whatever is buried in it. Given a deep open sandbed they work it all day, which is the reason to keep one — it is a fish that does something rather than hovers.

That same behavior is the catch. A goatfish will undermine rock stacked straight on the glass and will eat small worms, pods and tiny shrimp out of the bed, so it is poor company for a cleanup crew you paid for. Bare-bottom tanks are worse: nothing to sift, and a fish that stops feeding properly. If you are weighing the three tiers, the difference is set out here.