The OSFF (Oxymonacanthus longirostris) was thought to be an obligatory coral eater, but some people have had success weaning them onto prepared foods. Mine loves small mysis, enriched brine, Cyclopeeze, Nutramar Ova and NLS pellets. He's been in my tank softy reef for over two years.
Hopefully, the OP will have similar luck with his fish.