Acan Coral Care Guide (Acanthastrea and Micromussa)
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The short answer: Acans are beginner-to-intermediate LPS corals that do well in low to moderate light, roughly PAR 60–150, with low to moderate flow. Place them on lower rockwork or the sandbed, with space around them, because their fleshy polyps can extend feeder and sweeper tentacles when the lights dim. They are photosynthetic and also eager feeders; target feeding meaty foods 1–2x weekly is the most common routine.
Quick facts
| Topic | Acan |
|---|---|
| Care level | Beginner to Intermediate |
| Lighting | Low to Moderate |
| PAR guidance | PAR 60–150 |
| Flow | Low to Moderate |
| Placement | Lower rockwork or sandbed |
| Behavior | Fleshy polyps can extend feeder or sweeper tentacles, especially after lights dim. |
| Compatibility | Allow generous spacing to prevent stinging nearby corals. |
| Feeding | Target feed meaty foods 1–2x weekly |
Acanthastrea, Micromussa and "Asian" acans
"Acan" is the hobby name for a group of fleshy, colonial LPS corals with round, puffy polyps packed together on a stony skeleton. The best-known one, long sold as Acanthastrea lordhowensis, was reclassified by scientists as Micromussa lordhowensis; most reefers still just call it an acan or a "lord." Pieces sold as "bowerbanki" are another acan-type coral, long sold as Acanthastrea bowerbanki; scientists have since moved it to the genus Homophyllia, but the trade still calls it a bowerbanki or an acan. Trade terms such as "Asian acan" and "rainbow acan" describe where a piece came from or how it looks, not separate species.
The care below suits all of these. Small differences between pieces are normal, so watch how each one responds.
Light and placement
Acans prefer low to moderate light. Lower rockwork or the sandbed is the usual spot, out of the brightest area under the lights. In too much light, polyps tend to stay small and tight, and the tissue can pale.
When you add a new frag, start it at the low end of the PAR range or in a partly shaded spot, then raise it in small steps over a few weeks only if the polyps look full and healthy. A good sign is puffy polyps that cover the skeleton during the day. Leave room around each colony; acans spread outward as new polyps form, and their tentacles reach beyond the edge of the skeleton.
Flow
Low to moderate flow suits acans. They need enough movement to keep detritus from settling between the polyps and to carry food to them, but strong direct flow keeps the polyps deflated. If the polyps look pinched or stay small on the side facing a pump, reduce or redirect the flow. If debris collects on the colony, add a little more indirect movement.
Feeding
Acans get energy from light, but they are known as some of the most responsive feeders among LPS corals. Feeder tentacles usually come out when the lights dim, so feeding around or after lights out works well. Offer small meaty foods (finely chopped seafood, mysis or a fine coral food) 1–2x weekly. Turn the pumps off for a few minutes and release a small amount of food gently over each polyp.
Cleaner shrimp, peppermint shrimp and hermit crabs often steal food from LPS mouths. If that happens, feed the crustaceans first or cover the coral briefly with a cup or a feeding cone while it eats.
Water parameters
- Temperature: about 76–80°F
- Salinity: about 1.025–1.026 SG
- Alkalinity: about 7–11 dKH
- Calcium: about 400–450 ppm
- Magnesium: about 1250–1400 ppm
- Nitrate and phosphate: low but not zero; acans usually do better with measurable nutrients than in an ultra-low system
Stability matters more than a perfect number. Pick values inside these ranges and hold them steady; steady conditions are what keep acan polyps full.
Neighbors and spacing
Acans are not the most aggressive LPS corals, but they do sting. Their feeder and sweeper tentacles, which extend mostly after the lights dim, can damage nearby corals, and more aggressive neighbors such as Euphyllia, Favia, Favites and chalices can damage them in return. Allow generous spacing, and check the tank once after lights out to see how far each colony actually reaches.
Different acans placed side by side can also sting each other where they meet. Plan spacing for the colony's future size.
Common problems
- Polyps not inflating: usually flow that is too strong, light that is too strong, a recent parameter swing, or a neighbor stinging it. Check parameters and placement first.
- Tissue receding from the edge: often contact with an aggressive neighbor, detritus collecting on the colony, or instability. Reefers usually move it away from contact and improve gentle flow.
- Single polyps dying off: can follow injury, fish nipping or long-term stress. Many reefers dip the coral and watch the rest of the colony closely.
- Pale or white tissue: usually too much light after a move. Lower the coral or reduce intensity, then acclimate again more slowly.
- Fish picking at the polyps: some angelfish and other grazers pick at fleshy LPS. If a fish is the cause, the coral is unlikely to recover until it is separated from that fish.
How our listings work
TIA listings come in three kinds:
- WYSIWYG: The photo is taken individually, and you will receive the exact coral shown.
- Stock: The photo is a stock reference image; yours will be very similar.
- Cut to order: You receive a fresh-cut frag of about 1–2 inches from the colony shown; it will be very similar. Fresh-cut frags need at least 2 weeks to heal before they ship.
See the Help Center for shipping and arrival details.
FAQ
Are acans good for beginners?
Yes, they are often recommended as a first LPS coral. They prefer low to moderate light and flow, and they are forgiving in a stable tank.
Where should I put an acan in my tank?
On lower rockwork or the sandbed, in low to moderate light and flow, with space around it for its tentacles and future growth.
How often should I feed an acan?
Target feed small meaty foods 1–2x weekly, ideally when the feeder tentacles are out after the lights dim.
Is an acan the same as a Micromussa?
The coral long sold as Acanthastrea lordhowensis was moved to Micromussa. Most reefers still call it an acan, and the care is the same.
Why are my acan's polyps shrinking?
The usual causes are light or flow that is too strong, a recent parameter swing, or a stinging neighbor. Correct one thing at a time and give the coral several days to respond.