Velvet Horn Coral (Hydnophora exesa) Propagation Guide

How to propagate Hydnophora exesa (velvet horn coral): an easy-to-frag encrusting and branching coral, cut with clippers or a saw, but very aggressive with long sweepers.

Overview

Hydnophora exesa, the velvet or horn coral, is a stony coral in the family Merulinidae found in the oceans of north and east Australia, Southeast Asia, and East Africa. Its surface bears conical projections, called monticules, between short tentacles. Depending on tank conditions it grows as an encrusting form or as a branching one, both of which lend themselves to fragmentation.

Reproductive Mode

In aquaria Hydnophora is propagated asexually by cutting off branches or encrusting sections. Because it spreads across rockwork and branches readily, offending branches or sections can simply be cut off to make frags. It is among the easiest corals to frag and a fast grower that spreads quickly once established.

Fragging / Asexual Propagation

On branching colonies, select a branch; on encrusting colonies, choose a section growing over rock.
Cut off the branch or section with coral clippers, or use a saw on thicker pieces.
Work where the coral has spread so the parent keeps enough tissue to recover.
Glue or epoxy the frag to a plug.
Place it in moderate flow and moderate to high light, well away from other corals, to resume growth.

Cutting off sections is also how overgrowth is controlled, since Hydnophora spreads across rockwork and stings whatever it reaches.

Conditions for Propagation

Hydnophora requires moderate flow and moderate to high lighting, with care requirements similar to Euphyllia, and it will grow and spread under the right conditions. Stable temperature near 24-26 degrees Celsius, pH 8.1-8.4, and steady alkalinity, calcium, and magnesium support its fast growth.

Common Challenges

Hydnophora is very aggressive: both branching and plating forms can produce sweeper tentacles over five inches long that kill surrounding corals. Frags must be placed well away from neighbors, and the coral's tendency to spread across rock means it can overgrow and sting anything it contacts.