The St. Thomas Mushroom (Rhodactis sanctithomae) is a unique species. The surface of each mushroom is covered in large bulbs and can resemble a Bubbletip Anemone (Entacmaea quadricolor). They are delicate with thin tissue and should be under high indirect light.

These mushrooms are carnivorous and photosynthetic. While they will take food from the water column and even feed on larger items like brine shrimp, they benefit from higher lighting and will show brighter colors under more intense light. They should be given ample space in aquariums as they may damage other corals with prolonged contact. It is common for an individual mushroom to come off of a rock and settle somewhere else in the aquarium or for a mushroom to split into multiple mushroom to spread or start a new colony.