Knob Coral

About

Knob Coral (Dipsastraea helianthoides) is a large polyp stony coral that earns its common name from the raised, rounded corallites that give its surface a distinctly bumpy, almost nodular appearance. Each individual polyp sits within its own pronounced calyx, creating a pattern that sets it apart from the smoother faces of many other faviid-type corals. Coloration tends toward earthy greens, browns, and tans, sometimes with contrasting oral disc tones that become more visible when the polyps are extended and feeding. In the wild, this species is distributed broadly across Indo-Pacific reef environments, where it tends to occupy mid-reef zones with moderate water movement and diffuse to moderate light. In the aquarium, it behaves as you would expect from a large polyp stony coral in this family. It is photosynthetic, relies heavily on zooxanthellae for nutrition, and will also benefit from supplemental feeding with small meaty foods when the opportunity arises. It is reef safe and generally non-aggressive, though like most stony corals it can deploy sweeper tentacles at night, so give it reasonable spacing from neighbors. Intermediate care level is a fair assessment. It is not particularly demanding, but stable water chemistry and consistent conditions are important for long-term success.