A type of coral, button polyps get their name from their appearance. They are part of the zooanthus genus of corals and are primarily photosynthetic. They live on rock surfaces and do not require careful maintenance, so they are useful for artificial tank habitats.
These corals are round shaped with flattish tops on the ends of short stalks, which are attached to rock bases. The circular top has tentacles all around it. The polyps can be one of many colors, such as brown, yellow, or red. They look similar to sea anemones.
Button polyps are photosynthetic, which means that they can produce all the energy they need from sunlight and can become a brighter color if they receive a lot of light. The photosynthesis is mediated through the presence of zooxanthellae algae in the polyp, which acts as a symbiont, producing energy in return for a place to thrive. As well as the capacity for photosynthesis, the corals can obtain energy and nutrients from small marine life, such as plankton or brine shrimp. In nature, the button polyps collect this food as it drifts toward the polyps in the water current. The polyps do not attack larger organisms such as blenny fish, although larger organisms like crustaceans or butterfly fish can damage the polyps through nibbling on the ends of the tentacles.
Growth and spread of the button polyps occurs through budding off an existing polyp. The new bud, which is attached to the base of the first polyp, grows off and into a new adult polyp. A similar coral to button polyps, the Sea Mat looks superficially the same but can be differentiated through the presence of a large mat from which new polyps bud off, as opposed to the lack of a base mat that is characteristic of the button polyps. Button polyps tend to spread quickly and take over available space on the rocks in an aquarium.
Even though button polyps are not very fastidious in their environmental requirements, they do prefer to grow in water that does not move very quickly. As they are photosynthetic, they do best with a high level of light, but if they have to be kept at low-light levels, then the addition of plankton or other feed is advantageous. Artificial propagation is relatively simple as all that is necessary is to cut one polyp away from the original group, and this will attach to gravel under slow water flow conditions.