Common Micromussa Problems: Tissue Loss, Fading, Pests and Recovery

A Micromussa colony that suddenly recedes, pales out, or shows a strange organism at night can turn a proud tank centerpiece into a panic in a matter of hours. This guide walks through the most common symptoms in order — environment first, then pests, then infection — so you can identify the cause quickly and decide whether the coral is salvageable.

What You're Actually Keeping: Acan Lords vs. Micros

Micromussa was reclassified out of the genus Acanthastrea around 2016, but "Acan" remains the common trade name across the hobby, so you'll see both used interchangeably.

• Micromussa lordhowensis ("Acan Lords") — larger, fleshier polyps, often the more expensive show pieces.
• Micromussa amakusensis ("Micros") — smaller, tighter polyps, usually sold in bigger colonies of tiny heads.

Care requirements for both are nearly identical, so the troubleshooting below applies equally to either.

Baseline Parameters and Placement

Most Micromussa problems trace back to instability rather than a single "wrong" number. Keep these ranges steady rather than chasing a perfect reading:

Parameter	Target Range	Notes
Salinity	1.025–1.026	Stability matters more than the exact figure
Temperature	75–78°F (24–26°C)	Avoid swings during water changes
Calcium	400–450 ppm	Track alongside alkalinity, not alone
Magnesium	1250–1350 ppm	Low magnesium destabilizes calcium/alkalinity
Alkalinity	8–12 dKH	The single biggest driver of unexplained recession when it swings
Light	30–75 PAR	Low-to-moderate; most fading and tissue loss is from too much, not too little
Flow	Gentle-to-moderate, indirect	Enough to clear detritus, never a direct jet

Place Micromussa low-to-mid in the tank, on the sand bed or low rockwork, away from powerheads and away from aggressive neighbors — the same low-light, low-flow zone that keeps tissue extended and pigment stable.

How Much Light Is Really Safe

Sources disagree on the ceiling: some cap Micromussa around 25–50 PAR, others say a fully acclimated colony tolerates up to 75–100 PAR without issue. A practical middle ground is to start new frags at 30–50 PAR near the substrate and only nudge higher, gradually, if the coral shows good extension and coloration — there's no growth benefit to pushing light on a coral built for shaded reef zones. Acclimate new arrivals over 2–4 weeks; a sudden jump under strong LEDs is one of the fastest ways to bleach a healthy frag.

Tissue Recession: Ranking the Causes

When you see flesh receding from the skeleton, work through causes in this order of likelihood:

1. Unstable alkalinity/calcium — swings, not the absolute number, are the top cause.
2. Light shock — moving a frag too high, too fast.
3. Direct or excessive flow — tearing fleshy tissue or preventing polyp extension.
4. Neighbor aggression or allelopathy — stings or chemical warfare from nearby corals.
5. Elevated nitrate — especially climbing toward 30–50 ppm alongside rising phosphate.
6. Physical damage — from shipping, fragging, or an aquascape bump.
7. Infection — brown jelly taking hold in an already-stressed spot.

The Nutrient Balance Point

Micromussa handles mildly elevated nutrients better than SPS corals, but that tolerance has limits. Nitrate climbing toward 30–50 ppm — especially paired with unstable alkalinity — can trigger rapid recession; the instability seems to matter as much as the nutrient level itself. On the flip side, an ultra-low-nutrient ("too clean") system starves color and growth, leaving colonies pale and slow-growing. The target isn't zero nutrients — it's a stable middle ground.

Shipping Stress: The Overlooked Setup

A frag can arrive with tank parameters at your end perfectly fine and still be primed to fail weeks later. Temperature swings in transit, ammonia buildup inside a sealed bag, and prolonged time in the box all stress tissue before it even reaches your water. Acclimate slowly (drip or gradual temperature/salinity matching), skip the trip through bright light on day one, and expect a few days of retracted polyps as normal recovery — not a sign something in your tank is wrong.

Micromussa skeletons are also more porous and fragile than brain coral skeletons, which makes them more prone to breakage-triggered recession during fragging or an aquascape bump — handle colonies by the base, not the fleshy tissue.

Color Fading (Without Tissue Loss)

Fading that stops short of actual flesh loss is almost always lighting-driven:

• Too much intensity bleaches pigments toward pale or white.
• Insufficient blue spectrum or low nutrients dulls reds and oranges toward brown.

Color shifts can take anywhere from 24 hours to a couple of weeks to show fully after a lighting change, so give any adjustment time before deciding it didn't work.

Brown Jelly: The Emergency Scenario

Brown jelly infection is a fast-moving bacterial/protozoan infection that shows as brown, stringy, sloughing tissue with a foul odor. Left untreated, it can consume a colony in 24–48 hours, and it's contagious via water contact and drifting sloughed tissue.

Emergency response:

1. Physically isolate the coral immediately.
2. Use a turkey baster to blast the jelly off into a discard container — never let it drift onto neighbors.
3. Dip the coral in an iodine-based coral dip.
4. If recession is contained to one section, frag away the unaffected tissue with a clean cut.
5. Quarantine and re-dip over the following days to confirm it has stopped spreading.

Treatment and dip solutions can be browsed in Treatment › Medication if you need to restock before an outbreak happens.

A Quick Symptom Decision Tree

Use speed of spread, smell, and visible organisms to sort environmental issues from infection from pests:

Clue	Likely Cause
Slow recession over days-to-weeks, no smell	Parameter swing, light shock, or flow issue
Fast recession (hours), brown stringy tissue, bad smell	Brown jelly infection — act immediately
Missing polyp tissue overnight, no smell	Pest (flatworm, boring worm, or crab/hermit)
Recession only on the side facing another coral	Allelopathy or sting from a neighbor
Pale/white with intact tissue	Light shock or bleaching, not infection
Brown/dull with intact tissue	Lighting spectrum mismatch or low nutrients

Pests: What's Actually Bothering Your Micromussa

There's no single "obligate" pest that targets Micromussa the way Acropora-eating flatworms target SPS — but that doesn't mean pests aren't a real, recurring issue. Keepers commonly report:

• Predatory flatworms/polyclad worms grazing tissue at night.
• Boring/burrowing worms that tunnel into the skeleton, keeping the colony chronically unhealthy until physically removed.
• Small crabs or hermits picking at extended polyps.
• Vermetid snails or bristleworms irritating tissue with mucus nets or stings — more nuisance and competition than active predation.

Pest Protocol

• Quarantine every new coral for 2–4 weeks minimum.
• Dip new frags/colonies in an iodine or commercial pest dip before adding them to the display.
• Inspect at night with a flashlight — flatworms and boring pests are far more visible after lights-out.
• Repeat dips weekly for 3–4 weeks on anything found; dips kill the worms present but not their eggs.

A coral-safe dip and general water conditioners are worth having on hand — see Treatment › Water Condition & Additives for options.

Spacing and Allelopathy

Keep at least 4–6 inches from other corals, and 6–8 inches from Euphyllia species specifically — their sweeper tentacles extend well past the daytime skeleton at night and can sting Micromussa tissue on contact. Soft corals and leathers can also suppress nearby LPS through chemical warfare (terpenoids) even without physical contact. Unexplained recession on one side of a colony is worth checking against what's growing nearby before you look anywhere else.

Fragging and Post-Frag Care

If you need to frag a stressed or overgrown colony:

1. Use a sterile blade or coral saw and cut along skeletal ridges.
2. Dip the cut piece in an iodine solution immediately.
3. Place the frag in low light and moderate flow while it heals.
4. Avoid handling the healing tissue for 1–2 weeks.

Recovery Timeline

Healthy tissue can regrow over exposed skeleton within weeks once the stressor is removed. A colony that's lost most of its flesh needs weeks to months of stable, low-light, low-flow, well-fed conditions to fully recover. Not every recession is reversible — once it reaches the base or skeleton attachment point, that lobe is usually lost for good, even if the rest of the colony survives.

Feeding for Recovery

Underfed colonies lose color and growth even in clean water. Target or spot feed meaty foods — mysis, brine shrimp, chopped krill — 2–3 times a week, plus fine particulates for the smaller polyps. Reduce flow briefly during feeding so polyps can extend and grab food. Corals suited to this feeding style, along with the fine particulate foods that work well for smaller-polyp species, are worth browsing in Marine Livestock › Corals › LPS Hard Corals alongside your feeding supplies.

A Prevention Checklist

A short recurring routine catches most problems before they become emergencies:

• Weekly: test nitrate and phosphate; note any drift.
• Monthly: visual pest check with a flashlight after lights-out.
• Quarterly: flow and light audit — confirm nothing has crept up in intensity or placement.

Common Mistakes to Avoid

• Placing a new frag high under intense SPS-level lighting — the leading cause of bleaching and recession in new colonies.
• Blasting the coral with direct powerhead flow to "keep detritus off," which tears fleshy tissue instead.
• Chasing zero nitrate/phosphate in a mixed reef, which starves color and growth.
• Mistaking normal nighttime tissue retraction or a feeding-response color shift for disease.
• Skipping quarantine and dipping, introducing pests or infected tissue straight into the display.
• Placing Micromussa too close to Euphyllia or leathers, then blaming the Micromussa for "unexplained" recession.
• Ignoring an early, small patch of brown jelly instead of intervening within hours.

Frequently Asked Questions

Why is my Micromussa/Acan losing tissue from the base up?

Usually alkalinity swings, excess light, direct flow, or a slow infection. Check parameters and neighboring corals first, and act fast if you notice a brown, sloughing texture.

Can a Micromussa recover from tissue loss?

Yes, if the stressor is removed and the skeleton attachment point is still intact. Recovery can take weeks to months of stable low-light, low-flow, well-fed conditions.

Why did my Acan turn brown or dull instead of staying bright red/orange?

This is usually a lighting mismatch — too much intensity, or too little/wrong spectrum — or too-low nutrients. Give it 1–2 weeks after any lighting change before judging the results.

Is brown jelly disease contagious to other corals?

Yes, it can spread via water contact and drifting sloughed tissue. Isolate the affected coral immediately and prevent debris from reaching neighbors.

What's eating my Acan's polyps at night?

Most likely a flatworm, boring worm, or an opportunistic crab or hermit. Inspect with a flashlight after lights-out and dip the coral if you spot anything.

Do I need to quarantine and dip a new Micromussa frag?

Yes — quarantine for 2–4 weeks and dip in an iodine-type solution before adding it to the display, repeating weekly if any pest turns up.

Why is my Micromussa not extending its polyps?

Often excess flow, insufficient feeding, or recent stress from a move or relocation. Polyps commonly stay retracted for several days after any handling.

If you're ready to add a Micromussa colony or need dips and additives to support one you already have, browse LPS Hard Corals on FishyHub for current stock.