Acan Coral

Identity and scope

Common Name: Acan Coral

Scientific Name: Micromussa lordhowensis (formerly Acanthastrea lordhowensis)

Other Names: Acan Lord; Micromussa Lord; Lordhowensis Coral; Lord Coral

Family: Lobophylliidae

Coral Type: Large-polyp stony coral (LPS)

Native Range: Tropical Indo-Pacific, especially Australia and parts of Southeast Asia and the western Pacific

Overview

General Description: Acan Lord is the fleshy colonial stony coral Micromussa lordhowensis, formerly Acanthastrea lordhowensis. Other corals are also traded as acans. Ask about the individual colony's previous conditions and acclimate gradually rather than assuming equal hardiness or lighting tolerance.

Appearance: Colonies contain round, fleshy polyps with a central mouth and pronounced ridges or folds. Expanded tissue can conceal most of the hard skeleton, while feeding tentacles often become more visible after dark or when food is detected.

Color Variations: Available in red, orange, green, blue, purple, pink, yellow, teal, gray, and multicolored patterns. Lighting, nutrition, and stress can influence apparent color, and trade names are not reliable taxonomic identifiers.

Growth Form: Encrusting to massive colonial growth, with new polyps forming along the colony margin over a shared skeleton

Notable Characteristics: Its inflated polyps can look peaceful during the day, but the coral may digest or sting nearby tissue through nighttime tentacles or mesenterial filaments. The broad trade name 'acan' is also applied to other corals with different care and aggression.

Natural Habitat

Native Distribution: Indo-Pacific; M. lordhowensis is particularly associated with Australian reef regions, with records elsewhere in the western Pacific

Natural Reef Habitat: Often found on protected reef slopes and other lower-energy reef areas, including habitats where light may be reduced by depth or turbidity

Depth: Shallow to moderate reef depths; reported occurrence varies by locality

Natural Lighting: Exposure varies with identified species, locality, depth and water clarity. Natural-habitat descriptions are context, not a measured aquarium PAR prescription.

Natural Flow: Exposure varies by species, locality and reef position. A natural-flow description does not determine a universal aquarium pump setting.

Other Habitat Notes: Confirm the specimen's scientific identity when possible because Acanthastrea echinata, Micromussa amakusensis, and other corals may also be sold under the general 'acan' name.

Aquarium Placement

Recommended Placement: Begin on the sandbed or lower reef during acclimation. Move only if the coral remains well inflated, retains color, and receives an appropriate measured PAR level.

Space Requirements: Allow space for full polyp inflation, marginal growth, nighttime feeding structures, and defensive contact.

Rock/Sand Placement: Place on a stable, clean sandbed location or secure the exposed skeletal base to lower rockwork. Prevent sand from repeatedly collecting on the fleshy polyps.

Attachment Method: Secure the exposed skeletal base with reef-safe cyanoacrylate gel, epoxy putty, or a stable coral mount; never apply adhesive to living tissue.

Orientation: Keep the colony face upright or gently angled so sediment can clear and every polyp can expand without rubbing rock.

Distance From Other Corals: Leave clearance beyond the fully expanded colony and any observed defensive reach, including after dark and down-current. Add room for growth and neighboring aggression; no fixed separation guarantees compatibility.

Other Placement Notes: Avoid placing the colony beneath ledges that shed sediment or beside fast-growing corals that can shade or overtake it.

Lighting

Lighting Requirement: Use the retained provider-specific PAR example and gradual acclimation; a color name does not establish a universal lighting requirement.

PAR Range: There is no single verified PAR range for every Acan Lord specimen. Ask for the seller's measured conditions and acclimate gradually. Tidal Gardens reports 25-50 PAR for its Micromussa lordhowensis; use that as grower-specific context, not a requirement for every colony.

Spectrum Considerations: Ask about the seller's previous spectrum, measured intensity and photoperiod. Use appropriate reef lighting and make gradual changes; blue appearance, fluorescence or a color setting alone does not verify sufficient or safe exposure.

Acclimation Requirements: Ask about previous measured PAR, spectrum and photoperiod. Change exposure gradually with an adjustable fixture, shading or position, observing tissue and colony response; no fixed acclimation deadline guarantees success.

Signs of Too Much Light: Paling, bleaching, contraction or tissue deterioration after increased exposure warrant a lighting review, but are not light-specific diagnoses. Check water conditions, flow, physical injury, pests and contact damage before making repeated changes.

Signs of Too Little Light: Reduced growth or altered color can prompt a review of measured exposure and shading, but also has other causes. Compare with the colony's previous conditions and check chemistry, nutrition, flow and tissue condition rather than increasing light from appearance alone.

Water Flow

Flow Requirement: Provide enough indirect movement to clear sediment without deforming tissue. Tidal Gardens describes relatively low flow for its stock; this is grower context, not a pump-speed rule.

Preferred Flow Pattern: Provide adjustable broad indirect movement that clears debris and reaches the whole colony without pinning, abrading or tearing tissue. Reassess as the colony grows; qualitative flow categories are not universal pump settings.

Signs of Excessive Flow: Direct mechanical bending, tissue abrasion or continuous pinning warrants less direct exposure. Retraction or tissue loss alone is nonspecific; assess measured conditions and other possible irritants.

Signs of Insufficient Flow: Persistent debris or retained mucus warrants a circulation review. Poor expansion, color change or tissue decline has other possible causes and does not by itself prove inadequate flow.

Water Parameters

Temperature: OATA's large-polyp stony coral aquarium guide gives 24-26 degrees C as broad aquarium context, not a verified temperature optimum or tolerance limit for the identified Acan/Micromussa specimen. Maintain stable measured conditions, ask about the specimen's history and adjust gradually.

Salinity: OATA's marine-and-invertebrate aquarium example is 1.024-1.026 specific gravity: reef-system planning context, not a verified salinity optimum for the identified Acan/Micromussa specimen. Match established conditions with a calibrated instrument and check its temperature basis; no fixed SG-to-ppt conversion is assumed.

pH: OATA's large-polyp stony coral aquarium guide lists pH 8.1-8.3 as broad aquarium context, not a verified specimen limit for the identified Acan/Micromussa specimen. Its general marine setup sheet uses a different pH interval. Monitor pH with gas exchange and carbonate alkalinity; avoid abrupt corrections to force a number.

Alkalinity: OATA's large-polyp stony coral aquarium guide lists 8-12 dKH as broad aquarium context, not a required endpoint or dosing target for the identified Acan/Micromussa specimen. Measure carbonate alkalinity, keep changes gradual and consider nutrient conditions and observed response. dKH is not pH or freshwater GH.

Calcium: OATA's large-polyp stony coral aquarium guide lists 380-450 ppm calcium as broad aquarium context, not proof of a specimen-specific optimum or dosing requirement for the identified Acan/Micromussa specimen. Check actual system demand and measured trends before adjusting supplements.

Magnesium: OATA's large-polyp stony coral aquarium guide lists 1250-1350 ppm magnesium as broad aquarium context, not a verified specimen-specific optimum or automatic dosing instruction for the identified Acan/Micromussa specimen. Measure system conditions and verify any need before gradual adjustment.

Nitrate: Track nitrate with a reliable test alongside feeding, filtration and coral response. Avoid uncontrolled accumulation or abrupt nutrient stripping; no common optimal interval or diagnosis from one reading is established for every specimen in this guide.

Phosphate: Track phosphate, food input, algae and specimen response together. Avoid uncontrolled accumulation and abrupt stripping; a single low or high reading does not establish the cause of tissue loss, and no universal specimen-wide interval is prescribed.

Other Relevant Parameters: Use appropriate marine source water and routine system monitoring. Investigate ammonia or other abnormal readings rather than assuming a trace-element deficiency. Supplement only for a verified system need with suitable testing and product instructions; freshwater GH targets are inapplicable.

Parameter Sensitivity: Assess the actual specimen and measured system trends rather than assuming uniform tolerance. Avoid abrupt changes and review recent dosing, feeding, temperature, lighting, flow and handling when tissue or behavior changes.

Stability Requirements: Favor consistent measured marine conditions over repeated corrections. Verify surprising results, consider recent feeding, dosing and equipment changes, and adjust deliberately rather than changing chemistry, light and flow together.

Feeding & Nutrition

Photosynthetic: Yes; it hosts photosynthetic zooxanthellae

Natural Feeding: Uses light-derived energy and captures zooplankton, suspended organic matter, and small animals or food particles with feeding tentacles

Target Feeding: Optional but often beneficial. Feed only when tentacles or mouths respond, using a gentle pipette or baster and a small portion per polyp.

Recommended Foods: Finely chopped mysis shrimp, enriched brine shrimp, copepods, small marine pellets, or quality coral foods sized for the mouth

Feeding Frequency: No fixed schedule is established across the stated scope. If supplemental feeding is used, adjust small amounts to actual acceptance, uneaten food and measured nutrient trends; do not force-feed a stressed colony.

Benefits of Feeding: Grower observations can support optional feeding in their own stock, not a guaranteed improvement in growth, color or recovery for every specimen. Feeding does not substitute for appropriate lighting, measured water quality or health assessment.

Special Nutritional Requirements: Avoid placing oversized food on the colony or feeding every polyp heavily. Protect food briefly from fish or shrimp without enclosing the coral long enough to reduce oxygen exchange.

Growth

Growth Rate: Tidal Gardens reports relatively slow propagation and growth; do not predict a fixed rate for an individual Acan Lord.

Growth Pattern: New corallites and fleshy polyps develop around the outer margin as the shared skeleton encrusts outward.

Maximum Colony Size: No verified aquarium maximum is specified for Acan Lord here. Plan for outward colony expansion and review available space as polyps are added.

Space Requirements: Reserve room around the perimeter for new polyps and for defensive filaments or tentacles.

Overgrowth Concerns: It is not usually invasive, but the colony can encrust onto adjacent rock and damage neighboring corals as its edge expands.

Aggression

Aggression Level: Moderate

Sweeper Tentacles: Short feeding or sweeper tentacles may extend beyond the polyps, especially at night; extension varies by specimen.

Chemical Warfare: A dissolved-compound interaction is possible in a mixed reef, but this review does not establish a predictable chemical effect for every specimen or a guaranteed filtration remedy. Examine physical contact, shading and water conditions before attributing decline to chemical warfare.

Stinging Ability: Prevent contact with neighbors and assess the actual defensive reach. No fixed sting-strength grade establishes safe proximity or guarantees tolerance between colonies.

Required Spacing: Use the actual expanded footprint, observed nighttime reach, current direction and future growth to set clearance. No fixed inch-based starting distance is verified as universally protective.

Corals to Avoid Nearby: Avoid direct contact with SPS corals, zoanthids, chalice corals, other fleshy LPS corals, or any colony within reach of its expanding edge or filaments.

Compatibility

Fish Compatibility: Check the proposed fish's species-specific diet and behavior and observe the individual around this colony. A reef-safe sales label is not a guarantee; prevent persistent nipping, abrasion or physical displacement.

Invertebrate Compatibility: Assess the actual invertebrate's diet and behavior and secure the colony. Monitor food theft, irritation and displacement; a clean-up-crew or reef-safe label does not guarantee harmless contact.

Coral Compatibility: Mixed-reef suitability depends on the identified colonies' individual lighting, flow and growth needs plus separation from contact and defensive reach. Shared family or trade names do not establish safe touching or universal compatibility.

Potential Predators: Butterflyfish, some angelfish, filefish, and other coral-feeding species; individual behavior varies

Potential Irritants: Food-stealing shrimp or fish, sediment, vermetid snail mucus webs, algae touching exposed skeleton, persistent fish perching, and neighboring stings

Fragging & Propagation

Difficulty: Form- and specimen-dependent. Routine propagation of a healthy established colony is separate from treatment of unexplained tissue loss.

Propagation Method: Growers report captive fragmentation, but the appropriate method depends on species, form and healthy tissue layout. Obtain experienced form-specific advice; this guide does not prescribe cutting ahead of tissue loss as a universal rescue.

Tools/Method: Plan routine propagation with an experienced coral propagator, suitable tools, personal protection and containment of mucus, dust and spray. No cutting, antiseptic or dip is automatically indicated for a damaged or declining colony.

Healing: Keep any legitimately propagated fragment under stable, appropriately acclimated conditions and monitor attachment and tissue margins. Healing time and success vary; deterioration needs assessment rather than automatic repeated dips or cuts.

Special Risks: Handling, heat, crushing and torn tissue can damage a colony. Shared equipment or moving fragments can transfer unwanted organisms. Do not move apparently healthy pieces from a declining colony into another system as an assumed cure.

Safety Considerations: Use gloves and eye protection, protect skin cuts, contain mucus and skeletal dust or spray, and clean tools between colonies. Avoid improvised cutting of a deteriorating specimen; obtain experienced propagation or coral-health guidance.

Health & Common Problems

Tissue Recession: Record where tissue is missing, how quickly it changes and whether skeleton is exposed. Environmental instability, mechanical injury, contact damage, pests and infectious processes are possible, not diagnoses from appearance. Check measured conditions and recent changes; continued loss warrants qualified assessment.

Bleaching: Paling or whitening with tissue still present differs from bare skeleton after tissue loss. Heat and light stress are possible contributors, but appearance alone does not identify the cause. Verify conditions and recent exposure changes, correct confirmed problems cautiously and seek advice if deterioration persists.

Polyp Retraction: Retraction or deflation alone does not establish a cause. Compare with the colony's usual behavior, handling and light cycle; check measured conditions, flow, sediment, pests, injury and neighbor contact. Persistent closure with tissue deterioration warrants qualified assessment rather than automatic treatment.

Pests: Inspect actual tissue, margins, base and sheltered surfaces for organisms and damage, and identify suspected pests before treatment. Quarantine or separation can assist observation where safe. A dip is product-, coral- and pest-specific, not a universal cure; follow the exact current label and do not assume eggs or hidden pests are eliminated.

Diseases: Rapid or slow tissue loss, melting, or brown jelly-like material are observations, not proof of bacterial disease. Multiple environmental, physical, pest-related or infectious causes are possible. Document progression, verify measured conditions and obtain prompt coral-health or aquatic-veterinary guidance. Use safe matched-condition separation when practical; antibiotics, cutting, tissue removal and dipping are not universal or appearance-triggered treatments.

Signs of Stress: Persistent deflation, gaping mouths, unusual mucus, fading or bleaching, poor feeding response, tissue recession, exposed skeleton, or separation between tissue and skeleton

Common Keeper Mistakes: Placing the coral under intense light without acclimation, using strong direct flow, allowing sediment to accumulate, crowding neighbors, overfeeding, and confusing an aggressive Acanthastrea species with an Acan Lord

Recovery Considerations: Verify measured water conditions and recent changes, assess lighting, flow, injury, pests and neighbor contact, and correct confirmed problems cautiously. Avoid repeated moves or simultaneous large changes. Continuing or rapid tissue loss warrants prompt qualified advice; no automatic fragging, cutting, dipping or antibiotic protocol is prescribed.

Beginner Suitability

Beginner Friendly: Conditional on suitable measured marine conditions, gradual acclimation, growth space, observation and the ability to obtain qualified help; no uniform beginner-success guarantee is made.

Why: The grower describes low-light culture and small meaty-food feeding, but readiness still depends on stable measured conditions, gradual acclimation, spacing and observation; no beginner-success guarantee is made.

Major Challenges: Avoiding excessive light, balancing feeding with nutrient control, preventing sediment accumulation, and recognizing that not every coral sold as an 'acan' has identical behavior

Before You Buy

Important Considerations: Look for inflated, responsive polyps with tissue covering the skeleton to the colony edge. Avoid specimens with rapidly receding flesh, damaged mouths, brown jelly-like material, or heavy algae growing against exposed skeleton. Confirm the scientific or former trade identity if possible.

Space: Provide a stable lower placement with room for the colony to encrust outward.

Lighting: Ask for the seller's measured lighting and confirm that your fixture permits gradual acclimation; use the retained PAR example as provider-specific context.

Flow: Use gentle, indirect flow that keeps the colony clean without folding or abrading its flesh.

Aggression: Although less far-reaching than a Torch Coral, an Acan Lord can still damage neighbors through direct contact or mesenterial filaments.

Parameter Stability: Prepare an established, stable marine system with reliable monitoring appropriate to the actual colony and its neighbors. No trade-name-wide chemistry or detectable-nutrient threshold is established by this guide.

Long-Term Growth: Monitor actual marginal expansion and polyp addition. Growth speed and eventual space demand cannot be predicted from the acan trade name.

Species-Specific Information

Anything important that does not fit above: In current aquarium usage, 'Acan Coral' most often means Micromussa lordhowensis, the former Acanthastrea lordhowensis. The broader nickname may also refer to species that differ in polyp shape, aggression, and preferred placement. This guide focuses on the Acan Lord; confirmed identification should take priority over a seller's color-based trade name.

Related topics and compatibility

Similar Corals: Micromussa amakusensis, Acanthastrea echinata, Blastomussa species, Lobophyllia species, and other fleshy colonial LPS corals

Compatible Corals: Compatibility must be assessed for the actual colonies, with individual conditions, growth space and separation from observed contact or defensive reach; this is not a blanket safe-neighbor list.

Related Guides: LPS Coral Placement; Reef Aquarium Lighting; Coral Target Feeding; Coral Acclimation; Stable Reef Water Parameters; Blastomussa Coral Care