of the Month
Bob Goemans photograph by the author
Blue coral, ridge coral
Range: Western Pacific Ocean: south of
Japan, west to Africa’s east coast, and
throughout the Red Sea
Natural Environment: This
photosynthetic soft coral, the only member
of the order Helioporacea, is one of the few
soft corals that actually contribute to reef
building. It is quite abundant in the wild,
especially in brightly lit, shallow, intertidal
reef-flat areas, e.g., at 20 to 30 feet ( 6 to 9
meters) where there is exceptionally good
water movement, such as in and around areas that experience the continuous passing of waves overhead or the energy of
Its massive encrusting columnar and branching formations are often found along the upper reef slopes and upper
hardpan areas of lagoons. Its internal aragonite/calcium skeleton is sky blue, hence its most popular name, blue coral, due
to a concentration of iron salts it removes from surrounding seawater. It forms a hard outer crust of calcium carbonate that
is brown due to the zooxanthellae it houses.
Its small olive-colored polyps are interconnected by root-like extensions, called stolons, within its structure. It can shed
a layer of outer skin, similar to some leather and Porites corals, helping to remove unwanted coverings of algae and/or
bacteria. Usually found in various shades of brown or tan with white-tipped edges, which indicate new healthy growth.
Captive Care: This is a very hardy and disease-free coral, and quite common in the trade due to its abundance in the wild.
It requires strong light, and that coming from metal halides would be better than that of fluorescents, as several specimens
have shown in my systems. As for water movement, it should be placed where currents are fairly swift, yet not directly in
front of outlets where the force of the flow would damage its polyps. No special feeding is required for this photosynthetic
soft coral, but if placed in areas receiving inadequate light, the white edging of its branches that indicate new growth will
turn brown. This indicates that the coral is increasing its zooxanthellae numbers (which are brown) to satisfy its present
nutritional needs, therefore abandoning growth for the present.
The specimen seen here in my aquarium under metal halide lighting had doubled its size in only two years without any
special attention to its needs other than bright light and good water movement. Occasionally, this coral will shed a thin
layer of skin, a normal process, and I have used a turkey baster to completely remove any remaining pieces. Otherwise,
this soft coral, which actually feels like a stony coral, is exceptionally easy to maintain, given adequate light and water
Unfortunately, dried specimens are still sold in the ornament trade because of their blue coloring.
Water Quality Requirements: Calcium 380 to 430 ppm, alkalinity 3. 5 to 4.0 meq/l, pH 8. 1 to 8. 2, specific gravity 1.024
to 1.026, Mg approx. 1272 ppm, phosphate < .05 ppm, and a temperature range of 76° to 84°F ( 25° to 29°C).