Cynarina Coral

Cynarina is a stony coral made up of a single large polyp (solitary). During the day it fills its tissue with water and inflates; the swollen mantle becomes translucent and the thick, coarsely toothed septa beneath it look like the spokes of a wheel. In low light the mantle can expand to more than twice the size of the skeleton. The tentacles open only at night. Colors are mostly green and brown, but pink, red and two-tone individuals are also sold.

The base of the skeleton sometimes attaches to a surface and sometimes ends in a point, with the coral sitting free on the sand. Individuals reaching the trade are wild-collected and their trade is subject to CITES Appendix II; look for a maricultured individual if possible, otherwise choose one with untorn tissue that inflates readily.

It lives in sheltered reef environments and on deep sandy bottoms in the Indo-Pacific. It is not very common in the wild, but it stands out with its inflated mantle. Living in shaded, calm surroundings explains why it wants low light and gentle flow in the aquarium.

• Light: Low, about 50–100 PAR. In strong light the mantle does not inflate fully and the color fades.
• Flow: Low and indirect. Strong flow can tear the inflated mantle.
• Placement: On the sand or at the very bottom of the rockwork. If it falls from a height, its tissue is easily injured.
• Water parameters: Salinity 1.024–1.026, KH 7–10 dKH, calcium 400–450 mg/L, magnesium 1250–1350 mg/L. It is a tolerant species; after sudden changes it may not inflate for a few days. Nitrate 2–10 mg/L and phosphate 0.03–0.1 mg/L are suitable.

It is photosynthetic, but with its large mouth it makes very good use of supplemental food. Once or twice a week, when the tentacles open at night, place mysis, chopped shrimp or fish flesh on top of the mouth. Large pieces can be given, but too much food at once can leave the mouth gaping for days; small portions are safer.

It does not put out long "sweeper" tentacles, but with its night tentacles and mesenterial filaments it can burn a coral it touches. Since the inflated mantle also spreads out during the day, leave at least 10 cm of space. Do not place it within reach of aggressive LPS.

Dwarf angelfish, large angelfish and hermit crabs may pick at the mantle. Clownfish sometimes host in this coral and irritate the tissue.

Since it is a single polyp, it is practically never propagated in the aquarium; cutting it puts its life at risk. Almost all individuals sold are wild-collected. So when buying, make sure the whole skeleton is covered with tissue and that there are no tears or exposed skeleton.

• Mantle not inflating: Strong flow, too much light or a recent move are the most common causes; if it does not improve within a few days, move it to a shadier spot.
• Torn tissue and brown jelly: A wound from shipping or a fall can turn into an infection; if noticed early, give the coral a coral dip in a separate container.
• Mouth constantly gaping: A sign of overfeeding or stress.