Zoanthids

Class Anthozoa, Subclass Zoantharia, Order Zoanthidea

Common names: zoos, zoanthids, button polyps (sometimes inconsistently given names like "fire and ice" and "people eaters" based on phenotypic characteristics such as coloration and size that may have little or nothing to do with actual species identification)
Natural origin: wide-ranging, Indo-pacific
Sensitivity (Level 1): Zoanthids are usually quite tolerant and easy to care for.
Feeding: Appropriate food particle size depends on the size of the particular coral's polyp mouth size. Though usually not necessary, some aquarists target feed to encourage faster growth.
Lighting (Level 4 to 10): Though more intense lighting is usually preferred, many zoanthids can adapt to much lower light intensities. As with any zooxanthellate coral, coloration can change in response to changing lighting conditions.
Water flow: These corals do well with moderate to high water flow.
Placement: Though not aggressive corals, they are fast growing when healthy and need considerable space (like Xenia and star polyps, they can become a nuisance in tanks with slower growing stony corals competing for space).
General: Polyps will close at night and when stressed. They may take a few days (or even weeks) to open up in a new environment. WARNING: Zoanthids secrete a slime that is highly toxic to humans. It's wise to use gloves when touching these corals. Do not touch polyps if you have an open wound. Do not touch eyes or mouth after touching polyps.