Hairy Mushroom

The hairy mushroom is a mushroom coral that looks hairy because of the short tentacles with forked or branched tips that completely cover the disc surface. The disc is usually 5–10 cm across; in good conditions individuals over 15 cm are seen. Its color is mostly green, brownish green or gray; under blue light it glows fluorescent green. Most mushrooms sold in the trade as "hairy mushroom" are this species; whether it is the same species as R. rhodostoma, which is known from the Red Sea and sold in purple-toned forms, is debated.

Some individuals in the genus Rhodactis develop bubble-like swollen tentacles on the disc surface; these forms, sold in the trade as "bounce," are very expensive, and why the bubbles form is not fully understood. Mushroom corals are not covered by CITES.

It lives in groups on rock and rubble on the shallow reefs of the Indo-Pacific, in lagoons and in nearshore waters that occasionally become turbid.

• Light: Low to moderate light (about 50–150 PAR). In strong light the disc shrinks and the color fades.
• Flow: Low to moderate, indirect flow; strong flow can tear the tissue and detach the individual.
• Placement: The lower zone of the rockwork or shaded side surfaces.
• Water parameters: Salinity 1.024–1.026; KH 7–11 dKH. It likes water with some nutrients; 5–15 mg/L nitrate is not harmful.
• Relocating: Once it has attached well to the rock it is hard to remove; choose its permanent spot at first placement and, if necessary, move it together with a small rock.

It is photosynthetic, but a better hunter than Discosoma: it holds mysis, chopped krill or powdered food placed on the disc with its tentacles and digests it by closing its disc. Feeding small morsels 1–2 times a week noticeably speeds up growth.

It is considered one of the aggressive mushrooms: it can close its disc over small corals or frags next to it and burn them, shade them and gradually cover the rock. Keep it at least 10–15 cm away from stony corals and zoanthids; preferably grow it on its own rock.

It is compatible with fish and the cleanup crew; some dwarf angelfish may pick at the discs.

It multiplies on its own through pieces that break off the edge of the foot and by division. To propagate it by hand, the disc is cut in two or four with a scalpel and the pieces are kept in a container on small rocks, covered with mesh, until they attach; new individuals form within a few weeks.

• Shrunken disc: Too much light or flow; move the individual lower and into shade.
• Color fading: Very stripped water; raise nitrate and phosphate slightly and increase feeding.
• Detaching and wandering: Protect pump intakes with sponges.