Arnold's Stony Coral

About

Arnold's Stony Coral (Caryophyllia arnoldi) is a solitary cup coral native to the eastern Pacific, found within US coastal waters where it clings to rocky substrates in relatively cool, low-light conditions. Unlike many of the tropical stony corals that dominate the reef hobby, this species comes from temperate or deeper-water environments, which shapes everything about how you'd approach keeping it. It belongs to the genus Caryophyllia, a group of small, single-polyp corals that build compact, cylindrical skeletons. Modest in footprint but genuinely interesting up close, with tentacles that extend to reveal a textured, often translucent polyp. Because it does not rely heavily on zooxanthellae, feeding takes on greater importance than with many photosynthetic reef corals, and that's part of what puts it in the intermediate care bracket. Keepers should be prepared to target-feed regularly with meaty foods. It is considered reef safe, so it won't cause problems for tankmates, but its specific origin and likely preference for cooler, nutrient-available water means it fits better with an experienced keeper who can dial in and maintain stable, appropriate conditions rather than a standard tropical reef setup.