Rock Flower Anemone

With its flat, wide oral disc, the rock flower anemone looks like an open flower when seen from above. Many short tentacles line the edge of the disc; the bead-like bumps in the outer row explain the species' "beaded" name. Its colors are extremely variable: individuals in orange, red, green, blue and radiating mixtures of these are sold under trade names such as "Ultra" and "Green." The disc is usually 5–10 cm; the largest individuals reach 15 cm. In the hobby it is still mostly known as Epicystis crucifer; the currently accepted name is Phymanthus crucifer.

Staying small, usually remaining in place once settled and adapting to a wide range of lighting make it suitable for nano reefs. As a Caribbean species it is not a natural host for clownfish. Specimens in the trade are largely wild-collected.

It lives in the shallow waters of Florida, the Bahamas, the Gulf of Mexico and the Caribbean, in rock crevices or attached to stones beneath the sand. Its column stays inside the sand or crevice; only the disc opens at the surface. When disturbed it withdraws completely.

• Volume: at least 40 liters; a larger sand bed for several individuals.
• Placement: shaded corners where sand meets rock, vertical rock faces or flat stones under the sand. It chooses a suitable spot itself; once settled it rarely moves.
• Water: salinity 1.023–1.026 specific gravity, pH 8.1–8.4, temperature 23–27°C.
• Light and flow: moderate lighting and gentle to moderate flow are enough; under very strong light it protects itself by burrowing into the sand.
• Reef compatibility: Reef-safe with caution; it can sting nearby corals it touches, but its small size limits the effect.
• Acclimation and medication: Acclimate by the drip method for at least 1 hour; copper-based medications are lethal.

Carnivorous. It produces nutrients from light, but should be fed small morsels such as mysis, chopped mussel or shrimp 1–2 times a week. When a morsel is placed on the disc, the disc folds up and carries the food to the mouth in the center.

A calm, sedentary anemone. It opens its disc in the morning and closes it in the dark or when disturbed. It can catch very small fish and shrimp that bump into its disc.

Good companions: gobies, blennies, cardinalfish, clownfish; cleaner shrimp, snails, hermit crabs.

Avoid: butterflyfish and angelfish that pick at anemones; large crabs that walk over the disc; delicate corals placed too close.

It can be kept alone or in a group of several individuals; lining up individuals of different colors side by side is popular. They usually do not harm each other, but enough space should be left so that their discs do not overlap.

The sexes are separate. The male releases sperm into the water; fertilization takes place inside the female, who carries the young for a while. The tiny colorless anemones she releases settle around the mother and color up within a few weeks. Offspring are reported this way in mature aquariums where several individuals are kept together and well fed. It does not reproduce by splitting and cannot be propagated by fragmenting.

• Deflating: the disc may stay closed for a short time; if it does not open for days, the water parameters should be checked.
• Bleaching: fading color is a sign of light or temperature problems.
• Death: a dead anemone rots and pollutes the water; it must be removed immediately.

Cannot be told apart externally; an individual releasing sperm into the water is male, and one producing young is female.