Anthelia

Anthelia is a soft coral recognized by its long polyps rising from a thin basal mat (stolon) that spreads over the rock. Each polyp has eight long, feathery tentacles; these tentacles opening and closing in the current resemble waving fingers, which is why it is called "waving hand" in English. Its color can be white, cream, light blue, purple or pink. Although it resembles Xenia, its polyps do not pulse and do not form clusters at the tip of a single stalk; each polyp rises separately from the base.

In the trade it is mostly sold under the genus name only; identifying it to species level is difficult, and some colonies sold as "Anthelia" actually belong to other Xeniidae genera. It is an easy-care, hardy coral, and aquacultured pieces are common. Some members of this family have become invasive in seas they have been introduced to; do not release pieces or tank water into the wild.

In the Indo-Pacific and the Red Sea it forms extensive mats on the rocky bottoms of shallow reefs, on surfaces that receive light.

• Light: Moderate light (roughly 80–200 PAR). In aquariums with strong lighting, acclimate it lower down first.
• Flow: Moderate, variable flow. A gentle swaying of the tentacles is enough; in very strong flow the polyps do not open fully, and in very weak flow detritus builds up between the stalks.
• Placement: The middle part of the rockwork, preferably a stone separate from the main structure.
• Water parameters: Salinity 1.024–1.026; KH 7–11 dKH, calcium 400–450 mg/L, magnesium 1250–1350 mg/L. It reacts badly to rapid changes in KH and salinity.

It gets most of its nutrition from photosynthesis. Extra feeding is not required; very fine phytoplankton or powdered food can be given once a week. Overfeeding only increases algae.

It does not sting its neighbors and does not wage notable chemical warfare; its problem is that it spreads quickly over the rock with its basal mat and creeps in at the base of slow-growing corals. Keep it on a separate stone at least 15 cm from stony corals and trim the spreading edges regularly.

It is compatible with fish and invertebrates. Some dwarf angelfish and butterflyfish may pick at the polyps.

A piece of the basal mat is cut together with its polyps and attached to a small stone with a rubber band. Placing the piece on top of the stone and covering it with a mesh or a perforated cup for a few days also works. It attaches to the new surface within about a week. The colony also spreads sideways on its own.

• Polyps closed: Relocation, a sudden increase in light and KH swings are the most common causes.
• Melting: The sudden decline seen from time to time in the Xeniidae family can also happen to this coral; keep the water parameters stable.
• Uncontrolled spreading: Cut it back and remove it before it settles into the pores of the rock.