Black Sun Coral (related Tubastraea)
A variant of Dendrophyllia (Branching Sun Coral) (Dendrophyllia fistula)

Photo: Frédéric Ducarme · CC BY-SA 4.0
A related dendrophylliid with dark body and contrasting polyps; like Dendrophyllia it is azooxanthellate and must be fed individually. Note Tubastraea is invasive outside its native range—never release it.