Discosoma Mushroom

Discosoma mushroom corals belong to the order Corallimorpharia, which is related to stony corals but does not build a skeleton; they look more like a flattened anemone than a coral. Each individual consists of a short foot that clings to the rock and, on top of it, a flat, smooth or slightly bumpy disc 2–7 cm across. There is a small mouth in the center of the disc; the tentacles are very short and sparse. Their colors are extremely varied: metallic red, blue, purple, green, striped and spotted forms are sold.

The name Actinodiscus, once widely used in the trade, is today a synonym of Discosoma. Most mushrooms on sale are not identified to species; names such as Discosoma nummiforme are also often used loosely. Their care is the same, and because they multiply easily in the aquarium, captive-propagated individuals are common. Since mushroom corals are not stony corals, they are not covered by CITES.

• Red: The most common form, with metallic red or pink discs.
• Blue: A form with plain, deep blue discs.
• Striped: Light and dark bands running from the center outward on the disc.
• Spotted: Light-colored spots on the disc.
• Metallic and multicolored forms: Valuable captive-bred forms that glow under blue light and carry several colors.

In the Indo-Pacific and the Caribbean it lives in dense groups on rock and rubble on shallow reefs, in lagoons and in the shaded parts of reef slopes. Most adapt well to turbid, nutrient-rich water.

• Light: Low to moderate light (about 50–150 PAR). In strong light the discs shrink, the color fades and the individual may detach and move.
• Flow: Low to moderate, indirect flow. In strong flow it may let go of its foot and drift into a pump.
• Placement: The lower zone of the rockwork, shaded ledges or rocks near the sand.
• Water parameters: Salinity 1.024–1.026; KH 7–11 dKH. Slightly elevated nitrate (5–15 mg/L) and measurable phosphate are usually good; in very stripped water the discs shrink and lose their color.

It gets most of its nutrition from zooxanthellae and also absorbs dissolved substances and fine particles from the water. Supplemental feeding is not needed; a small mysis shrimp or powdered food placed on the disc once a week can speed up growth.

Its sting is weak, but it spreads as it multiplies, shades neighboring corals with its discs and can make their tissue recede where it touches them. Leave at least 10–15 cm of clear space from stony corals and keep the mushrooms in their own area. Different mushroom species live side by side without problems.

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

It multiplies on its own in the aquarium: small pieces break off the edge of the foot and become new individuals, or the individual splits in two down the middle. To propagate it by hand, the disc is cut in two or four with a scalpel; the pieces are kept in a container on small rocks covered with mesh until they attach. To remove an individual stuck to the rock, you need to cut under the foot with a sharp knife.

• Shrunken discs: The most common cause is too much light or strong flow; move the mushroom lower.
• Color fading: Very stripped water; raise nitrate and phosphate slightly.
• Detaching and wandering: The mushroom leaves an unsuitable spot and looks for a new one; protect pump intakes with sponges.