Acropora Corals

What are Acropora corals?

Acropora is the largest genus of stony corals and the one most associated with advanced reefkeeping. Colonies are built from many small polyps over a branching skeleton, with a distinctive axial corallite at the tip of each branch driving extension. They grow faster, color more intensely, and fail more dramatically than any other coral group, which is why a thriving acropora display is treated as the benchmark for a well-run system. They are the most demanding of the SPS corals.

Acropora growth forms

Acros are grouped by how they branch, and the form affects both placement and difficulty:

• Staghorn and slimer types — open, widely spaced branches, the fastest growing and most forgiving. The right place to start.
• Tenuis — delicate, flat-topped branching with fine tips, prized for pastel coloration and generally more demanding.
• Tortuosa and tight-branching morphs — dense, thick branches holding deep blues and purples, slower growing and highly collectible.
• Tables and plates — horizontal growth spreading into a flat disc, which needs open space and unobstructed light above.

Acropora care: stability above everything

High light, strong turbulent flow, and low nutrients are the usual targets, but stability matters more than any single number. Alkalinity is the parameter to watch: a swing of one dKH within a day can trigger tissue loss across an entire colony. Most successful acropora keepers dose continuously rather than relying on water changes, and test frequently with dependable water testing equipment. Review your reef lighting coverage before adding frags, and raise new pieces into high light gradually rather than placing them at the top on day one.

Pests and tissue loss

Acropora attract pests that other corals do not, and an unexplained decline is often a pest problem rather than a chemistry problem. Red bugs, acropora-eating flatworms, and montipora nudibranchs on neighbouring corals all cause the pale, closed polyps and gradual recession that keepers first blame on parameters. Dip every new frag before it enters the display, inspect branch bases under magnification when a colony stops extending polyps, and treat the whole system rather than a single colony when you find something.

Working up to Acropora

Most successful acropora tanks were montipora and birdsnest tanks first. Those corals teach you what stable alkalinity looks like on your own system at a fraction of the cost. Compare montipora corals and birdsnest corals as a starting point, see the whole group in SPS corals, or browse established pieces in coral colonies.