Blastomussa

Blastomussa merletti

The low-light gem — fat, glowing polyps that colour up best OUT of bright light.

Difficulty: BeginnerLPS coral

Blastomussa (Blastomussa merletti, "blasto") is the low-light gem of the LPS world — clusters of fat, fleshy, jewel-toned polyps that glow deepest reds, greens and oranges precisely because they DON'T want bright light. It's a hardy, peaceful, beginner-friendly coral: give it low light, gentle flow, a couple of feeds a week and stable water, and it colours up beautifully.

Good to know: LOW light (too much bleaches it); gentle flow; feed the hungry polyps.

📊 What keepers actually ask: Bought for colour, like the acan; the recurring "my blasto bleached / lost colour" issue is almost always too much light.

Care at a glance

Colony / form	Clusters of rounded fleshy polyps on a shared base; spreads polyp by polyp.
Lighting	LOW — around 50–100 PAR. Too much light bleaches it and washes out the colour.
Water flow	Gentle to moderate, indirect — its fleshy polyps dislike strong flow.
Placement	Lower to mid rock or the sand, in a shaded, low-flow spot.
Temperature	75–82°F (24–28°C).
pH	8.1–8.4.
Specific gravity	1.023–1.026 (reef-standard ≈35 ppt).
Other targets	LPS build a stony skeleton — keep alkalinity (≈8–11 dKH), calcium (≈400–450 ppm) and magnesium (≈1300–1450 ppm) stable.
Feeding	Photosynthetic PLUS meaty foods 1–2× a week — the fleshy polyps feed readily and grow faster for it.
Growth & spread	Steady — adds polyps to form a colourful cluster; easy to frag.
Natural range	Indo-Pacific.

Beginner-friendly, done right. A hardy, peaceful, beginner-friendly LPS whose one rule is light: blasto is a LOW-light coral (≈50–100 PAR), and too much light bleaches it and strips the very colour it's prized for. Keep it low and shaded, give it gentle flow (strong flow bothers the fleshy polyps), feed it a meaty morsel once or twice a week, and hold alk/Ca/Mg stable. It's semi-peaceful — give it a little space, but it lacks the long sweepers of Euphyllia.

Keep those numbers steady. This coral's alkalinity, calcium and magnesium only keep it safe when they're stable. If one reads low, our free reef dosing calculator works out exactly how much to add for your water volume — and splits it safely over days.

Where does it go? Light, flow and placement make or break a coral. Our free coral placement guide shows the PAR, flow and tank zone this coral wants — and what else thrives in the same spot.

The fish store gets these wrong

Common myths, kindly corrected — no shame for having believed them.

"More light = better colour." The opposite for blasto — it's a low-light coral, and bright light bleaches it. Keep it shaded and low for the best colour.
"LPS all want strong flow." Blasto's fleshy polyps dislike strong flow — keep it gentle so the polyps inflate.

Before you buy

A LOW-light, shaded spot (≈50–100 PAR).
Gentle flow and a little space from neighbours.
Stable alk/Ca/Mg; meaty foods to feed it.

Signs something's wrong

A struggling coral is almost always telling you about light, flow or water — here's what to watch for:

Fading or bleaching colour — too much light; move it lower or shadier.
Polyps not inflating — too much flow, or a chemistry issue.
Receding tissue or exposed skeleton — a parameter swing or infection; check water.

Never

Never keep blasto in high light — it bleaches.
Never blast it with strong flow (fleshy polyps).
Never let alkalinity swing.

Common blastomussa questions

Why did my blastomussa lose its colour or bleach?

Almost always too much light. Blasto is a low-light coral (around 50–100 PAR), and bright light bleaches it and washes out the deep colours it's collected for. Move it lower and shadier and it usually recovers.

How much light does blastomussa need?

Low — roughly 50–100 PAR. It colours up best in shaded, lower-light spots; strong light is the main way keepers lose its colour.

Is blastomussa a good beginner coral?

Yes — it's hardy, peaceful and forgiving, with fat fleshy polyps that feed readily. The one rule is keeping it in low light and gentle flow.

Do I need to feed blastomussa?

It's photosynthetic but has hungry, fleshy polyps that take meaty foods readily — feeding once or twice a week promotes growth and colour.

Is blastomussa aggressive to other corals?

It's fairly peaceful — it lacks the long stinging sweepers of Euphyllia — but give it a little space as it spreads polyp by polyp.

Sources & further reading

This guide was written and fact-checked against these authorities. It's honest, general guidance — not a diagnosis, and not a substitute for an aquatic vet or your own test kit:

Reef Chasers — Blastomussa Coral Care Guide — low light, flow, feeding
Whitlyn Aquatics — Blastomussa Coral Care — PAR, placement, feeding
Extreme Corals — Blastomussa Care Guide — lighting, flow, feeding

Written and fact-checked by The Coralkin Team against marine-aquarist sources — if your blastomussa is struggling, it's almost always a light, flow or water-chemistry issue — check those first and ask an experienced reefer. We never guess a care number.

🔬 Review status: team-written and fact-checked against cited sources · not yet reviewed by a marine vet. How we research & fact-check →

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