This fan is usually seen on vertical walls of the outer reef in depths between 10-30 m (33-100 ft). The colonies form an intricate network of rectangular meshes attain- ing their largest size and most spectacular growth forms in places where currents are especially strong. In prim positions these fans are up to 2-3 (6-10 ft) high and measure more than 3-4 m ft) in width. The fans project from the reef s surface at angles offer. ing maximum exposure to the prevailing current, which supplies nourishment in the form of plankton Color usu ally ranges from cream to pale pinkish orange. One vari ety s red color i due to a thin algal coating Alcyo narians rarely harbor encrusting organisms such as algae, sponges, and sea squirts as their abundant feeding polyps and vari- ous chemical secretions help to repel an wanted coloniz- ers Medical researchers are analyzing the chemical make- of these species an attempt to di ver substances that hit cancer and other diseases