Coral care guide
Acan & Micromussa Coral Care Guide
Bright, fleshy, and usually hungry, the corals reef keepers call “acans” are some of the most rewarding LPS in a mixed reef. Give them stable water, sensible light, room to inflate, and the occasional meal. They will handle the rest.
They are forgiving, not immortal. The skeleton keeps receipts.
First: what counts as an acan?
“Acan” is a hobby name, not a precise modern identification. Many of the round-polyped corals historically sold as Acan Lords are now classified as Micromussa lordhowensis. True Acanthastrea species, including Acanthastrea echinata, also remain in the hobby and may still be labeled simply as acans.
The trade name is useful when shopping, but care should follow the coral in front of you. Watch its tissue inflation, feeding response, coloration, and reaction to flow instead of trying to force every acan into one rulebook.
Quick care guide
| Requirement | Recommended starting point |
|---|---|
| Care level | Easy to moderate |
| Lighting | Low to moderate; roughly 50–120 PAR |
| Flow | Low to moderate, indirect, and varied |
| Placement | Lower to middle reef; secure and clear of aggressive neighbors |
| Feeding | Optional but beneficial; small meaty foods 1–2 times weekly |
| Temperature | 76–79°F |
| Salinity | 1.025–1.026 specific gravity |
| Alkalinity | Approximately 8–9 dKH, kept stable |
| Calcium | Approximately 400–450 ppm |
| Magnesium | Approximately 1,250–1,400 ppm |
| Nutrients | Detectable nitrate and phosphate; avoid sudden swings or bottoming out |
These are starting points, not commandments carved into a frag plug. Stability and the coral’s response matter more than chasing one perfect number.
Lighting
Most Micromussa and common acans do well under low-to-moderate light. A range around 50–120 PAR is a practical starting point, with new arrivals beginning toward the lower end. Increase intensity slowly only after the coral is consistently inflated and feeding.
Too much light too quickly can cause paling, bleaching, or a tightly retracted appearance. Too little light may produce darker tissue, reduced growth, or muted coloration. Spectrum matters too: fluorescent greens, oranges, and blues will look very different under heavy actinic lighting than under a whiter daytime spectrum.
Our product photos show the actual coral under blue reef lighting unless a listing says otherwise. Color in your aquarium will depend on spectrum, intensity, nutrients, camera processing, and viewing method.
Water flow
Use low-to-moderate indirect flow. The goal is enough movement to keep debris from collecting between polyps without forcing the tissue tight against the skeleton.
A healthy acan should be able to inflate normally. If one side stays compressed, the flesh whips sharply, or the coral never expands, redirect the pump or move the frag. If waste consistently settles on it, add a little more varied flow rather than blasting it from one direction.
Placement and spacing
The lower half of the reef is usually a sensible starting location. Place the coral on a stable surface where snails, fish, or normal maintenance will not knock it into a neighbor. Avoid sharp rock that can cut inflated tissue.
Give acans several inches of space and check the reef after lights-out. Some extend feeding or defensive tentacles farther than expected, and Acanthastrea echinata can be particularly unfriendly to nearby corals. “It looked far enough away during the day” is a classic reef-keeping sentence for a reason.
Feeding
Acans are photosynthetic, but occasional direct feeding can support fuller tissue and faster growth. Offer small portions of mysis, finely chopped krill, quality frozen blends, or appropriately sized LPS pellets once or twice per week.
Reduce flow while feeding and give each polyp time to close around the food. Resume normal circulation after roughly 10–15 minutes. Food should be small enough to swallow easily. More food is not automatically more growth; excess can be rejected, decay in the rockwork, or push nutrients higher than intended.
Water chemistry and stability
Acans need the same stable foundation as other stony corals: consistent salinity, alkalinity, calcium, magnesium, and temperature. Rapid alkalinity or salinity swings are generally more damaging than sitting slightly outside a fashionable target range.
Keep nitrate and phosphate detectable rather than stripping the aquarium completely clean. Extremely low nutrients can contribute to pale tissue and poor resilience, while chronically high nutrients can suppress coloration and encourage algae around exposed skeleton. Make corrections gradually.
Acclimating a new acan
- Inspect the coral and plug for pests, eggs, damaged tissue, and nuisance algae.
- Follow a trusted coral-dip protocol and the product’s directions. Never expose fleshy LPS tissue to freshwater.
- Begin in lower light with gentle, indirect flow.
- Allow the coral to settle before feeding heavily or moving it repeatedly.
- Increase light only after normal inflation and feeding response are established.
A recently shipped acan may remain partially deflated for a short period. Look for steady improvement rather than demanding maximum inflation on day one.
Reading the coral
Healthy signs
- Full, fleshy polyps without exposed skeletal edges
- Regular inflation and a clear feeding response
- Stable coloration appropriate to the aquarium’s spectrum
- New tissue or small developing polyps around the colony edge
Warning signs
- Tissue staying tightly retracted against the skeleton
- Fresh recession or exposed white skeleton
- Rapid paling or bleaching
- Brown jelly-like material, foul tissue, or fast tissue loss
- Repeated damage along the side facing a pump or neighboring coral
Troubleshooting
| Symptom | Check first | Practical response |
|---|---|---|
| Stays deflated | Direct flow, recent handling, unstable salinity or alkalinity | Reduce direct flow, stop moving it, and verify stability |
| Pale or bleaching | Recent light increase or very low nutrients | Reduce intensity and make gradual corrections |
| Darker or muted color | Low light, elevated nutrients, or spectrum differences | Confirm parameters, then adjust light slowly |
| Receding tissue | Injury, aggression, instability, pests, or infection | Isolate the cause quickly and protect healthy tissue |
| Algae on exposed skeleton | Existing tissue loss plus excess light or nutrients | Correct the cause of recession and carefully keep the skeleton clean |
| Refuses food | Stress, excessive flow, oversized food, or daytime feeding response | Try smaller food after lights dim and reduce flow briefly |
Rapid tissue loss is not a “wait and see for a week” problem. Separate the coral from possible aggressors, verify water chemistry, and inspect it closely.
Can acans change color?
Yes. Light intensity, spectrum, nutrients, feeding, and stress can all change how an acan appears. A coral photographed under blue LEDs may look less fluorescent under a white-heavy spectrum without being unhealthy or inaccurately represented.
Judge long-term health by tissue coverage, inflation, feeding response, and growth—not by whether the coral matches a phone screen under completely different lighting.
Final take
Start an acan in modest light and indirect flow. Keep the reef stable, leave room for inflation and aggression, feed small portions when useful, and adjust based on the animal rather than the label. That approach works better than chasing a universal acan formula because there is no universal acan.