How Fast Do Blastomussa Grow? Growth Rates and Tips for Better Color

Blastomussa is a large-polyp stony (LPS) coral that grows by slowly budding new heads rather than spreading tissue across the rock like a soft coral. Expect roughly 1 to 4 new polyps every 2 to 3 months under solid conditions, with growth and color quality tied to the same handful of variables: feeding, light, flow, and parameter stability.

How Blastomussa Actually Grows

Unlike zoanthids or soft corals that carpet a rock through lateral tissue spread, Blastomussa (commonly sold as B. wellsi or B. merletti) grows through budding — an existing polyp splits or produces a new head next to itself, each with its own distinct skeleton wall (corallite). Over time, a single head becomes a cluster, and a cluster becomes a colony.

This is a fundamentally slower growth style than SPS corals, which lay down calcium carbonate in branching or encrusting sheets. It's also different from many massive LPS species that grow as one continuously expanding mass. Blastomussa's polyp-by-polyp budding means growth looks "lumpy" — a new head appears, then nothing visible happens for weeks, then another head appears.

What to expect, realistically:

• Short term (2–3 months): 1 to 4 new heads on a healthy, well-fed frag.
• Medium term (1 year): roughly 1 inch (2.5 cm) of added colony diameter, though this varies a lot by specimen and care.
• Long term (1–3 years): a 3–4 polyp frag can become a small colony of 6–7+ heads spanning 8–12 inches (20–30 cm) across with consistent feeding and stable water quality.

Because individual polyps are fleshy and large — typically 1–2 inches (2.5–5 cm) across when fully open, sometimes bigger — even a colony with a modest head count can look full and impressive. Don't judge growth purely by visual "coverage"; count heads and track corallite formation instead.

Sources disagree on the exact numbers, and that's expected for a coral this slow. Some frame growth purely in new-head counts, others in colony diameter per year, and some skip a numeric claim altogether. Treat any single figure as a rough benchmark, not a guarantee — genetics, feeding consistency, and parameter stability matter more than any fixed growth rate.

Water Parameters for Steady Growth

Stability matters as much as the exact numbers. A parameter that swings within its "acceptable" range still stresses budding more than a parameter held steady at the low or high end.

Parameter	Acceptable Range	Ideal Target
Temperature	72–84°F (22–29°C) tolerance	76–82°F (24–28°C)
Salinity (SG)	1.023–1.026	~1.025 (~35 ppt)
pH	8.0–8.4	8.1–8.3
Alkalinity	8–12 dKH	8–10 dKH, held steady
Calcium	400–450 ppm	~420 ppm
Magnesium	1250–1350 ppm	~1300 ppm
Nitrate	2–10 ppm	5–10 ppm
Phosphate	0.03–0.1 ppm	0.05–0.1 ppm

Note the nutrient ranges: unlike SPS corals, Blastomussa doesn't want nitrate and phosphate scrubbed to zero. Some measurable nutrient level supports color and budding; an ultra-clean system with near-zero nutrients tends to starve growth and pale the tissue out.

Lighting Deep Dive

Blastomussa is one of the more shade-tolerant LPS corals in the hobby, which makes it forgiving to place — but also easy to overdrive with modern high-output fixtures.

PAR targets:

• Outer tolerance range: 50–150 PAR
• Best growth and color: roughly 75–100 PAR for most LED setups

By light type:

• LED fixtures: because output is concentrated and easy to ramp up, start Blastomussa low or mid-tank and dial intensity down before adjusting placement. A colony under a strong LED often needs 12–18 inches of water column, or a shaded rock ledge, to land in the target range.
• T5 fluorescent: T5 output is more diffuse, so mid-tank placement under a full T5 fixture is usually closer to the target range without extra tinkering, though bulb age and count still shift actual PAR.

Signs of too much light: bleaching or washed-out, pastel coloration; polyps staying retracted or only partially expanding during the day; tissue paling from the outer edge inward.

Signs of too little light: dull brown or muddy coloration from excess zooxanthellae; slower-than-expected budding despite good feeding; polyps that expand fully but never develop saturated color.

Placement: lower to mid tank, ideally on a shelf or ledge that's shaded from the most intense part of the light path. If moving a frag from a dim frag-tank setup into a brighter display, acclimate gradually — a dark start followed by a light ramp over 1–2 weeks protects the tissue from a bleaching event that can also stall growth for months while the coral recovers.

Water Flow Guidance

Blastomussa wants low, indirect, turbulent flow — enough movement to keep detritus off the fleshy polyps and to help deliver food particles, but never a direct current.

Practical ways to achieve this:

• Place the colony behind rockwork so it receives flow that has already bounced and diffused, not a direct line from a powerhead or return nozzle.
• Position it off to the side of a wavemaker's throw, not in the direct path.
• Watch polyp behavior: fully expanded, gently swaying polyps indicate good flow; polyps that stay clamped shut or look tattered at the edges indicate flow that's too strong.

Direct blasting flow is one of the most common reasons a Blastomussa colony looks "dead" even though it's alive — chronic retraction from strong current prevents the polyps from ever expanding, which in turn prevents feeding, coloring up, or budding.

Feeding Guide

Feeding is the single biggest lever a hobbyist controls over both growth rate and color intensity. A colony run on light alone will grow far slower and duller than one that's target-fed regularly.

What to feed: small meaty foods sized for a 1–2 inch polyp — mysis, baby brine shrimp, marine snow-type blends, or coral pellets formulated for LPS. Larger, more established colonies can also take a phytoplankton supplement to support incidental feeding of the surrounding tissue and any resident pods.

How often: 2–3 times per week is a practical baseline; some hobbyists feed every other day and see faster results, provided nutrient export (protein skimming, water changes) keeps pace.

Technique:

1. Turn off flow in the area for 15–30 minutes before feeding so tentacles can fully extend.
2. Use a pipette or turkey baster to place small amounts of food directly onto or just above each polyp's tentacles.
3. Give the polyp time to capture and pull food in before moving to the next head.
4. Restore flow gradually once polyps have closed back around their meal.

Overfeeding risks: dumping excess food into the display instead of target-feeding invites nuisance algae, aiptasia, and other pest blooms as uneaten particles decay. Feed only what individual polyps can actively capture, and increase frequency rather than volume if you want to push growth faster.

Color Variety and What Caps It

Blastomussa is sold in a wide range of color morphs, including green, red or orange, teal-centered, "watermelon" (green body with red or pink centers), and multi-tone "rainbow" combinations. These morphs are visually distinct enough that color alone is often how frags are marketed.

What's less discussed: genetics set a ceiling on ultimate color saturation. Two frags cut from different mother colonies, kept under identical parameters, lighting, and feeding, can plateau at noticeably different intensities — one reaching a vivid, saturated hue and the other staying comparatively muted no matter how well it's cared for. Good husbandry lets a coral reach its genetic potential; it doesn't override that potential. If a frag's color seems capped despite textbook conditions, the mother colony's lineage — not your setup — may be the limiting factor.

Hobbyists shopping for a specific color intensity can browse current LPS coral listings to compare morphs before choosing a frag.

Placement and Tank Size

• Clearance: give each head at least 2 inches (5 cm) of space from neighboring corals. Blastomussa is moderately aggressive — it extends sweeper tentacles at night that can sting slower-growing or stationary neighbors, and crowded frags will shade or out-compete each other, stalling growth on the affected side.
• Substrate: place on a flat rock ledge or frag plug, never buried in or resting directly on sand — sediment settling on the fleshy tissue leads to irritation and tissue recession over time.
• Tank size: a 20–30 gallon tank comfortably houses a frag or small grouping. A 40+ gallon tank gives an established colony room to bud outward for years without needing to be fragged purely for space. A single frag can also work in a 10–20 gallon nano tank, provided flow and lighting stay in range.

Fragging and Propagation

Once a colony has several heads with clearly visible, separate skeleton walls between polyps — generally after a year or more of healthy growth — it's ready to frag.

Tools needed: a coral saw or bone shears, a fresh blade or clean cutting edge, and an iodine-based coral dip.

Process:

1. Identify the natural corallite divisions between heads — cutting along these lines, rather than through a polyp, keeps each frag intact.
2. Cut cleanly with the saw or shears.
3. Dip each frag in iodine solution per the product's instructions to reduce infection risk.
4. Place cut frags in low flow and moderate light (toward the lower end of the PAR range) to heal.

Recovery timeline: healing typically takes 1 to 3 weeks before the frag resumes normal growth. During this window, skip target feeding directly on the cut edge and keep flow gentle until tissue has fully closed over the exposed skeleton.

Common Mistakes to Avoid

• Direct flow blasting the colony, causing chronic retraction that looks like a dead or dying coral even though it's alive.
• Skipping acclimation when moving a frag from a dim tank into a brighter display, leading to bleaching within days.
• Never target feeding and expecting SPS-style growth from lighting alone — Blastomussa needs the extra energy input from meaty foods.
• Crowding frags too close together, so sweeper tentacles sting neighbors and stall growth on the affected side.
• Running nutrients too low. A pristine, near-zero nitrate and phosphate system starves color and slows budding — some nutrient availability is beneficial for this coral, unlike for SPS.
• Mistaking slow, lumpy budding for stagnation and making unnecessary parameter or lighting changes when the colony is actually progressing normally.
• Ignoring tissue recession (flesh pulling back from the skeleton), which usually signals unstable alkalinity, calcium, or magnesium, or a bacterial issue — test water immediately and consider an iodine dip if recession continues.

Why Patience Matters More Than Any Single Number

Because Blastomussa grows so slowly, a single week or even a single month of observation rarely tells you whether a change worked. A parameter adjustment, a new food, or a lighting tweak needs roughly 8 to 12 weeks before you can fairly judge its effect on budding rate or color.

Two habits make this manageable:

• Photograph monthly, from the same angle and distance, rather than relying on memory. Side-by-side photos reveal new heads and color shifts that are easy to miss day to day.
• Change one variable at a time. If you adjust lighting and feeding frequency in the same week, you won't know which one drove the result 10 weeks later.

A mature, well-established tank also helps in a way that's easy to overlook: biofilm and pod populations built up over time provide incidental grazing between manual feedings. For a slow accumulator like Blastomussa, this background food source matters more than it does for fast-growing corals that rely primarily on light.

Frequently Asked Questions

How long does it take a Blastomussa frag to grow into a full colony?

Roughly 1 to 3 years from a small 3–4 polyp frag to a solid colony of 6 or more heads, assuming steady feeding and stable parameters. Genetics and consistency of care both affect where in that range a given frag lands.

Why is my Blastomussa not growing new heads?

The most common causes are insufficient target feeding, lighting that's either too weak or too strong, unstable alkalinity, calcium, or magnesium, or flow that's too strong and keeps polyps closed. Rule these out one at a time and give at least 8 weeks before judging a fix.

What makes Blastomussa lose color or turn brown?

Excess light bleaches a colony toward white, while too little light combined with high nutrients causes browning from excess zooxanthellae. Dial lighting into the moderate 75–100 PAR range and keep nitrate and phosphate stable rather than near zero.

How often should I feed Blastomussa for best growth?

Two to three times weekly with small meaty foods like mysis or coral pellets is a practical baseline. Pause flow for 15–30 minutes during feeding so tentacles can fully extend and capture food.

What PAR or lighting does Blastomussa need?

The tolerance range is roughly 50–150 PAR, but best color and growth typically come around 75–100 PAR for most LED setups. Start on the lower end and adjust based on polyp expansion and coloration over several weeks.

Can Blastomussa go in a nano tank?

Yes, a single frag suits a 10–20 gallon (38–76 liter) nano tank as long as flow stays gentle and lighting stays in range. As the colony buds outward over time, it will eventually need more real estate than a nano tank provides.

Is Blastomussa aggressive toward neighboring corals?

Moderately. It extends sweeper tentacles at night that can sting nearby corals, so keep at least 2 inches (5 cm) of clearance between heads and any neighboring colony.

How do I know when to frag my Blastomussa?

Once individual heads show clear, separate skeleton walls and the colony is crowding its allotted space — typically after a year or more of healthy growth — it's ready to cut along the natural corallite divisions.

If you're ready to start or expand a Blastomussa colony, browse current frags and colonies in FishyHub's LPS coral category, or explore the broader coral selection to plan out a reef that grows steadily over the next few years.