Blastomussa Wellsi

Blastomussa wellsi is known in the hobby simply as "Blasto." The colony consists of polyps 1–1.5 cm across sitting on short tubes (corallites). During the day the polyps open not tentacles but an inflated mantle; as the mantle expands it merges with neighboring polyps and the skeleton is completely hidden. The mantle is mostly dark gray, red or green, while the mouth area glows in a different color.

Its ability to thrive in low light, its peaceful nature and how easily it is fragged make it well suited to mixed reef tanks. As a stony coral, its trade is subject to CITES Appendix II; aquacultured frags are common, so choose those. Its small-polyped relative Blastomussa merleti is a separate species.

• Red Blasto: Dark red mantle, often with a green mouth.
• Green Blasto: Green mantle and a paler mouth area.
• Two-tone (bicolor) Blasto: Forms in which the mantle and mouth are clearly different colors.

It lives from the Red Sea to the Western Pacific on lower reef slopes sheltered from waves and in turbid waters; it is rare in the Red Sea. The fact that it is usually found in shaded, calm places in the wild explains why it wants low light and gentle flow in the aquarium.

• Light: Low to moderate, about 50–120 PAR. In strong light the mantle does not open and the color fades.
• Flow: Low and indirect. The mantle should ripple gently; in strong flow the polyps shrink.
• Placement: The lower part of the rockwork, a shaded recess or a rock on the sand.
• Water parameters: Salinity 1.024–1.026, KH 7–10 dKH, calcium 400–450 mg/L, magnesium 1250–1350 mg/L. Tolerant apart from sudden changes. A little nitrate (2–10 mg/L) and phosphate help keep the mantle full.

It is photosynthetic; even in low light it gets a significant part of its nutrition from symbiotic algae. It makes good use of supplemental feeding: once or twice a week, after the lights go out and the polyps have opened, place fine-grained LPS food, mysis or chopped brine shrimp on the polyps. Fed colonies produce new polyps more often.

It is a peaceful LPS; it does not put out long stinging tentacles. Even so, tissue loss can occur at the border with a coral it touches directly, so leave about 5 cm of space. It is itself easily harmed by aggressive species such as Euphyllia, Galaxea and Favites; do not place it within their reach.

Dwarf angelfish and some hermit crabs may pick at the mantle. It lives without problems alongside clownfish and most reef fish.

It is easy to propagate. Because each polyp sits at the tip of its own tube, one or several polyps are cut from the base of the tube with coral cutters and glued to a frag plug. Single-polyp frags survive too, but pieces of 3–5 polyps grow faster. New polyps bud from the edges of existing polyps.

• Mantle not opening: The most common causes are too much light, strong flow and a recent move; move the colony to a shadier spot.
• Tissue recession at the base of the polyps: Detritus collecting at the base of the tubes or insufficient flow can cause it; blow the detritus away with a pipette.
• Color loss: Seen after a sudden increase in light; raise the light gradually over weeks.