Acan Coral

Micromussa lordhowensis

Jewel-toned fleshy polyps in every colour — collectible, hardy and easy to feed.

Difficulty: Beginner–IntermediateLPS coral

Acans (Micromussa lordhowensis, long known as Acanthastrea) are collectible, jewel-toned LPS — fleshy discs of polyps in almost every colour, prized and fragged like currency. They're hardy and easy to feed, want lower light and gentle flow, and have one caveat: sweeper tentacles that make them semi-aggressive to close neighbours.

📊 What keepers actually ask: Acans are bought for COLOUR, so the recurring pain is “my acan lost its colour / bleached” — almost always too much light. We lead with the low-light requirement.

Care at a glance

Colony / form	Fleshy polyps packed into a colourful colony; grows outward polyp by polyp and is easy to frag.
Lighting	LOW — around 25–50 PAR. Acans are very light-responsive: colour shifts noticeably with light, and too much bleaches them. Keep them shaded/low.
Water flow	Moderate, not too strong — their flesh is delicate and tears/recedes in harsh flow.
Placement	Lower rock or the sand in a shaded, moderate-flow spot — and give it SPACE: acans have sweeper tentacles and can take feeding aggression out on close neighbours.
Temperature	75–82°F (24–28°C).
pH	8.1–8.4.
Specific gravity	1.023–1.026 (reef-standard ≈35 ppt).
Other targets	LPS build a stony skeleton — keep alkalinity (≈8–11 dKH), calcium (≈400–450 ppm) and magnesium (≈1300–1450 ppm) stable.
Feeding	Loves meaty foods — small pieces of mysis, krill and the like (small mouths, so keep pieces small). Feeding drives both growth and colour.
Growth & spread	Steady; adds polyps outward. Highly collectible and easy to frag once established.
Natural range	Indo-Pacific, including Australian waters.

Beginner-friendly, done right. Hardy and rewarding, with two things to respect: they're low-light corals (25–50 PAR — too much bleaches them and washes out the colour they're prized for), and they're semi-aggressive, extending sweeper tentacles and taking feeding aggression out on neighbours. Give them a shaded, moderate-flow spot with space, feed them, and they colour up beautifully.

Keep those numbers steady. This coral's alkalinity, calcium and magnesium only keep it safe when they're stable. If one reads low, our free reef dosing calculator works out exactly how much to add for your water volume — and splits it safely over days.

Where does it go? Light, flow and placement make or break a coral. Our free coral placement guide shows the PAR, flow and tank zone this coral wants — and what else thrives in the same spot.

The fish store gets these wrong

Common myths, kindly corrected — no shame for having believed them.

“More light = better acan colour.” The opposite — acans are low-light corals (25–50 PAR); too much light bleaches them and washes out the very colours they're collected for. Keep them shaded and low.
“Acans are totally peaceful because they're fleshy LPS.” Not quite — they're semi-aggressive, with sweeper tentacles and feeding aggression that can harm close neighbours. Give them space.

Before you buy

Pick a LOW-light, shaded spot (25–50 PAR) — key to keeping their colour.
Moderate (not strong) flow — their flesh is delicate.
Leave space from neighbours (sweeper tentacles).
Have small meaty foods ready — feeding drives colour and growth.

Signs something's wrong

A struggling coral is almost always telling you about light, flow or water — here's what to watch for:

Fading or bleaching colour — almost always too much light; move it lower/shadier.
Receding flesh or exposed skeleton — too much flow, a chemistry swing, or feeding aggression from a neighbour.
Not opening / staying deflated — check flow (too strong?) and water stability.

Never

Never keep acans in high light — it bleaches them and kills the colour.
Never blast them with strong flow (delicate flesh).
Never crowd them against other corals — the sweepers sting.

Common acan coral questions

Why is my acan coral losing its colour or bleaching?

Almost always too much light. Acans are low-light corals (around 25–50 PAR) and are very light-responsive — too much bleaches them and washes out the colours they're prized for. Move them lower and shadier.

How much light do acan corals need?

Low — around 25–50 PAR. They colour up best in shaded, lower-light spots; strong light bleaches them.

Do acan corals need to be fed?

They love it — offer small pieces of meaty food like mysis and krill (their mouths are small, so keep pieces small). Feeding drives both growth and their intense colour, on top of photosynthesis.

Are acan corals aggressive?

Semi-aggressive — they extend sweeper tentacles and can take feeding aggression out on close neighbours, so give them space from other corals.

Are acans (Acanthastrea) the same as Micromussa?

Yes — the coral long sold as Acanthastrea lordhowensis has been reclassified as Micromussa lordhowensis. "Acan" is still the common hobby name.

Sources & further reading

This guide was written and fact-checked against these authorities. It's honest, general guidance — not a diagnosis, and not a substitute for an aquatic vet or your own test kit:

Saltwater Aquarium Blog — Acan Coral Care Guide — placement, feeding, growth, aggression
Tidal Gardens — Micromussa Coral Care — light/PAR, flow, feeding, taxonomy
Bulk Reef Supply — How to Care for LPS Corals — LPS chemistry, feeding

Written and fact-checked by The Coralkin Team against marine-aquarist sources — if your acan coral is struggling, it's almost always a light, flow or water-chemistry issue — check those first and ask an experienced reefer. We never guess a care number.

🔬 Review status: team-written and fact-checked against cited sources · not yet reviewed by a marine vet. How we research & fact-check →

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