Velvet Horn Coral

Care at a glance

Overview

Keep it in a stable reef of 100 liters or more with strong light, brisk flow, and reef chemistry held near calcium 420 ppm, alkalinity 8 to 11 dKH, temperature 24 to 27 C, and pH 8.1 to 8.4. It feeds mostly through photosynthesis but accepts tiny meaty foods. This is one of the more aggressive corals in the trade, extending sweeper tentacles up to 7 cm after dark that can kill or badly sting anything nearby, so give it at least 15 to 20 cm of clear space on all sides.

In the wild

A branching stony coral covered in small cone-shaped bumps called hydnophores, which give the surface a velvety, thorny texture. Most aquarium colonies are bright neon green, though brown and cream forms exist. It grows as upright antler-like branches and adds height quickly once settled. The tissue is thin and fuzzy, with polyps that extend a soft fur of tentacles during the day.

Good to know

Hydnophora rigida sits in the family Merulinidae. The raised monticules on its branches are a defining trait of the genus, formed where the walls of neighboring corallites meet. It is a small polyp stony coral that builds an aragonite skeleton and hosts zooxanthellae.

Did you know

Its stinging sweepers are potent enough that hobbyists often keep it well away from prized colonies until they learn exactly how far it can reach at night.

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