Elephant Ear Mushroom

The elephant ear mushroom is the largest species in the order Corallimorpharia. The disc is usually 20–25 cm across and in good conditions can reach 30 cm or more. Its color is brown, greenish or gray; there are short tentacles along the edge of the disc and small bumps on its surface. Although it looks calm, it is an effective predator: when a fish touches its disc or tries to rest on it, it lifts its edges within a few seconds, turns into a sac and traps its prey inside. This behavior is mostly seen at night.

Thanks to its photosynthetic symbiotic algae it does not depend on hunting and is easy to care for; the real issue is choosing the right tankmates. Mushroom corals are not covered by CITES.

It lives singly or in small groups on hard bottoms between sand and rock on shallow reefs, in lagoons and on sheltered fringing reefs of the western Pacific.

• Light: Low to moderate light (about 50–150 PAR). It is not as light-sensitive as other mushrooms, but opens best in moderate light.
• Flow: Low, indirect flow; the broad disc closes or detaches in strong flow.
• Placement: The lower zone of the rockwork or a broad, flat rock near the sand. Account for the area the disc will cover when fully open.
• Volume: At least 200 liters because of the disc size.
• Water parameters: Salinity 1.024–1.026; KH 7–11 dKH. It is tolerant of nutrients.

It is photosynthetic but also digests morsels it catches or that are placed on it. Once a week, small morsels such as mysis, chopped shrimp or fish flesh can be placed in the center of the disc; the disc closes and wraps around the morsel. Heavy feeding is not necessary.

For neighboring corals the main dangers are shading and burns where its disc touches; leave at least 15 cm of clear space around it. For fish, however, it is a real predator: small fish that rest near the bottom or the rocks, such as gobies, cardinalfish, small blennies, damselfish and clownfish, can be caught. The safest option is to keep it in a dedicated mushroom tank or only with large fish.

Shrimp and snails can also be caught when they land on the disc. Some dwarf angelfish may pick at the disc.

In the aquarium it occasionally multiplies through pieces that break off the edge of the foot or by splitting. To propagate it by hand, the disc can be cut in two with a scalpel; the pieces are kept in a separate container in low light until they attach. Because of the thick tissue, healing after cutting can take weeks.

• Disc constantly closed: Strong flow or too much light; move it to a lower, calmer spot.
• Small fish disappearing: This may be the result of nighttime hunting; move small fish to another aquarium.
• Detaching and wandering: Protect pump intakes with sponges; a large disc that gets stuck to a pump is seriously damaged.