Why do my Rainbow Acanthastrea (Micromussa lordhowensis) polyps swell during the day but recede at night?

This species often “puffs up” under comfortable PAR and stable alkalinity, then extends feeding tentacles after lights dim. If nighttime retraction persists, flow may be too turbulent, or pests like vermetid snails are irritating tissue. Try gentler, indirect flow, feed small meaty foods 1–2 hours after lights out, and inspect for filaments from vermetids near the colony.

My rainbow colors are fading toward a single hue—what factors cause color shifts in M. lordhowensis?

Spectrum and nutrients drive pigments. Blue-violet heavy light supports fluorescence, while excess white or very high PAR can wash colors. Ultra-low nitrate/phosphate also dulls hues. Aim for moderate PAR (80–150), stable nitrate 5–15 ppm, phosphate 0.03–0.1 ppm, and gradual acclimation to any light change. Trace elements (iodine/iron) help, but avoid dosing blindly—confirm with tests.

How does this coral grow, and can I guide its shape on the rockwork?

It starts encrusting, then forms plump mounding heads. Provide a flat or gently sloped surface so new corallites grow evenly, avoiding shadowed valleys that trap detritus. Spacing of 2–3 inches limits border wars. If you want a plate-like colony, mount on a larger tile and keep flow steady but not blasting to prevent lopsided growth.

The coral is receding from the edges despite “normal” parameters—what uncommon issues should I check?

Look for alkalinity micro-swings (daily 0.5+ dKH shifts), abrasive sand contact, and stings from hidden sweepers of nearby LPS. Vermetid mucus threads and hydroids can cause chronic irritation. Consider a broad-spectrum bacterial dip if you suspect brown-jelly onset. Improve detritus export under the colony, and raise nocturnal pH drift with a reverse-lit refugium or kalkwasser if safe.

Rainbow Acanthastrea Coral

Overview

Rainbow Acanthastrea Coral features thick, fleshy polyps with multi-colored ringed patterns. Micromussa lordhowensis is a large-polyp stony coral forming clustered heads, suited to moderate light and low to moderate, gentle water flow. It is photosynthetic with symbiotic algae and benefits from occasional small meaty feedings to support growth and color. Place on stable rock or sand with space from neighbors, as sweeper tentacles can sting nearby corals.

Quick Facts

Care Moderate

Lighting Low–Moderate

Flow Low–Moderate

Placement Low–Mid

Temperament Semi-aggressive (3–6 inches spacing)

Recommended Parameters

Temp 76–80°F

pH 8.1–8.4

Salinity 1.025–1.026

Calcium 400–450 ppm

AlkAlkalinity 8–9 dKH

Magnesium 1250–1350 ppm

Feeding photosynthetic, mysis shrimp, enriched brine shrimp, copepods, rotifers, finely chopped seafood (shrimp, clam), zooplankton, microplankton, coral-specific powdered foods

Care & Placement

Rainbow Acanthastrea Coral (Micromussa lordhowensis) thrives with stable, moderate conditions and gentle care. Provide low to moderate light (PAR ~50–120); start shaded and increase over 2–3 weeks to prevent bleaching. Use low to moderate, indirect flow—just enough to keep debris off the flesh without causing tissue to peel. Target feed 2–3 times weekly after lights down with small meaty foods (mysis, chopped shrimp, pellet) to support growth and coloration; watch for feeder tentacles to extend. Keep parameters steady: temperature 75–79°F (24–26°C), salinity 1.025–1.026 (35 ppt), pH 8.1–8.4, alkalinity 8.0–9.5 dKH, calcium 400–450 ppm, magnesium 1250–1350 ppm. Allow some nutrients: nitrate 5–15 ppm, phosphate 0.03–0.10 ppm. Test weekly and adjust slowly; this coral is sensitive to rapid changes, especially in alkalinity and light.Place on the sandbed or lower rock ledges with 2–3 inches of space from neighbors. It is semi‑aggressive and can extend short sweepers at night, so avoid close placement with other fleshy LPS. Acclimate with a 30–45 minute drip and a brief pest dip before mounting. Avoid sharp rock edges and abrasive sand movement around the base. Siphon detritus nearby to prevent recession. If tissue pulls back, check for salinity or alkalinity swings, excessive light, or pests (vermetids, flatworms); correct gradually. Use activated carbon for chemical warfare in mixed reefs, maintain clean but not sterile water, and observe nighttime polyp extension as a simple health check.

FAQ

Frequently Asked Questions

About the Rainbow Acanthastrea Coral

Why do my Rainbow Acanthastrea (Micromussa lordhowensis) polyps swell during the day but recede at night?

This species often “puffs up” under comfortable PAR and stable alkalinity, then extends feeding tentacles after lights dim. If nighttime retraction persists, flow may be too turbulent, or pests like vermetid snails are irritating tissue. Try gentler, indirect flow, feed small meaty foods 1–2 hours after lights out, and inspect for filaments from vermetids near the colony.
My rainbow colors are fading toward a single hue—what factors cause color shifts in M. lordhowensis?

Spectrum and nutrients drive pigments. Blue-violet heavy light supports fluorescence, while excess white or very high PAR can wash colors. Ultra-low nitrate/phosphate also dulls hues. Aim for moderate PAR (80–150), stable nitrate 5–15 ppm, phosphate 0.03–0.1 ppm, and gradual acclimation to any light change. Trace elements (iodine/iron) help, but avoid dosing blindly—confirm with tests.
How does this coral grow, and can I guide its shape on the rockwork?

It starts encrusting, then forms plump mounding heads. Provide a flat or gently sloped surface so new corallites grow evenly, avoiding shadowed valleys that trap detritus. Spacing of 2–3 inches limits border wars. If you want a plate-like colony, mount on a larger tile and keep flow steady but not blasting to prevent lopsided growth.
The coral is receding from the edges despite “normal” parameters—what uncommon issues should I check?

Look for alkalinity micro-swings (daily 0.5+ dKH shifts), abrasive sand contact, and stings from hidden sweepers of nearby LPS. Vermetid mucus threads and hydroids can cause chronic irritation. Consider a broad-spectrum bacterial dip if you suspect brown-jelly onset. Improve detritus export under the colony, and raise nocturnal pH drift with a reverse-lit refugium or kalkwasser if safe.