Plate Coral

The plate coral is a plate- or disc-shaped, single-polyp stony coral that lives on the sand without attaching to rock. On its upper surface, radial septa run from the slit-like mouth in the center to the edge; during the day this surface is covered with short, pointed tentacles. By inflating its body with water it can move very slowly, right itself if it is flipped over and shake off sand that piles up on top of it. In the wild it can reach 28 cm; individuals of 10–20 cm are usually sold in the trade.

Its name should not be confused with the soft "mushroom corals" (corallimorphs such as Discosoma); this species is a true stony coral with a skeleton. Its trade is subject to CITES Appendix II. Besides wild-collected individuals, maricultured ones are also available; choose those.

It is common on reef slopes and the sandy bottoms of lagoons from the Red Sea to the Central Pacific. When young it is attached to the bottom by a stalk; as it grows it breaks off its stalk and begins to live free.

• Light: Moderate, about 75–200 PAR. An open area on the sand that the light reaches is suitable.
• Flow: Low to moderate and indirect. Strong flow can roll the coral over or tear its tissue.
• Placement: Always on the sand. If placed on rock, it slides, falls and is injured on sharp edges.
• Water parameters: Salinity 1.024–1.026, KH 7–10 dKH, calcium 400–450 mg/L, magnesium 1250–1350 mg/L. It is tolerant; what matters most is stability. Nitrate 2–10 mg/L and phosphate 0.03–0.1 mg/L are suitable.

It is photosynthetic, but becomes fuller and more colorful with supplemental feeding. Once or twice a week, place mysis, chopped shrimp or LPS food near the mouth; the tentacles slowly carry the food to the mouth. Since the mouth is in the middle of the body, offering food right in the center is the easiest way.

Although its tentacles are short, they sting, and because the coral moves around it can reach its neighbors over time. Keep it at least 10–15 cm away from other corals on the sand; leave distance from corals at the base of the rockwork as well. Do not place it next to aggressive LPS on the sand such as the elegance or open brain coral.

Dwarf angelfish and some hermit crabs may pick at the tissue. Clownfish sometimes host in this coral.

The most common way it reproduces in the aquarium is through small buds (anthocauli) that form on the skeleton of injured or stressed individuals. After a while these buds break off the parent skeleton and begin to live free. It is also known to be propagated by cutting the disc into wedges, but this is risky and requires experience.

• Tissue loss at the edge: Usually rubbing against rock or glass, sharp rock edges or an injury from a fall.
• Getting buried in sand: Animals that stir the sand can cover the coral; check on it regularly.
• Tissue not inflating: A sign of strong flow, a sudden change in lighting or starvation.