St. Thomas Mushroom

Rhodactis osculifera

Also known as Rhodactis sanctithomae, Discosoma sanctithomae, Warty Corallimorph

SaltwaterCoral

Care at a glance

Temperature: 75–81°F (24–27°C)
pH: 8.1–8.4
Adult size: 3.9 in (10 cm)
Minimum tank: 11 gal (40 L)
Temperament: Peaceful
Social behavior: Solitary
Swim level: Bottom
Difficulty: Beginner
Breeding: Medium
Rarity: Common
Reef safe: Reef safe
Origin: Caribbean
Family: Discosomidae

Overview

An easy corallimorph for moderate light around 75 to 150 PAR and gentle to moderate indirect flow, placed low on the rockwork or on rubble where it can attach and spread. It is low sting and safe near most neighbors, though a spreading patch will slowly claim rock, so give it its own zone. Occasional feedings of small meaty foods speed up splitting, which is how it multiplies in the tank.

In the wild

The St. Thomas mushroom lives on shallow rock and rubble across the Caribbean, Bahamas and Florida, sometimes as single polyps and sometimes carpeting a patch of reef. Its disc is covered in rounded, bubble-like vesicles rather than the fine fuzz of Pacific hairy mushrooms, and pieces come in reds, greens and blues, often with an iridescent sheen. It favors calm, slightly shaded spots over bright exposed rock.

Good to know

Rhodactis osculifera is a corallimorph in the family Discosomidae, a soft bodied relative of stony corals with no skeleton. It spent decades in the trade and field guides as Rhodactis sanctithomae or Discosoma sanctithomae, names now treated as synonyms of the older Rhodactis osculifera. It relies mainly on zooxanthellae and also takes small meaty particles that settle on the disc.

Did you know

The bubbly vesicles across its disc get this mushroom mistaken for a small bubble tip anemone often enough that some Caribbean suppliers sell it under exactly that comparison.