Knopia is a genus of Stolonifera soft corals closely related to Clavularia. They occur in the Indo-Pacific, the type specimen is from Malaysia, and other occurrences are documented for example in Indonesia. In contrast to Tubipora and Clavularia, the tentacles are not feathered with individual branchlets, but fused and paddle-like. One can see very nicely by it that the tube coral belongs to the Octocorallia, i.e. the eight-rayed flower animals, because each polyp forms 8 of these "paddles".
The species is zooxanthellate and feeds on light. The genus name is a dedication to the German marine journalist Daniel Knop. Knopia is a monotypic genus with the only species Knopia octocontacanalis. The color is usually brown-gray, with a fluorescent green-yellow oral disc in the center. It can spread quickly and should better be placed separately from the reef structure to avoid overgrowth.