The Harlequin or Orange-spotted filefish (Oxymonacanthus longirostris) from the Indo-Pacific is truly stunning, displaying a psychedelic livery of orange spots on a bright green background.
It’s also a specialist feeder, being an obligate corallivore feeding exclusively in the wild on SPS coral polyps — specifically Acropora. This diet means this species is difficult to maintain long-term and I suspect that dismal survival rates are the norm. Although some have maintained Harlequins by providing adequate Acropora, or by weaning them on to substitute feeds — and they have even been captive bred — success stories are rare.