Healing & Grow-Out

A frag is not a finished thing; it is a starting point. What happens in the weeks and months after the cut — how the wound heals, how the frag grips its plug and begins to encrust, how fast it grows into a colony — is where propagation actually pays off. This chapter covers the recovery process, honest growth expectations, and how to run a grow-out system that turns one frag into a shelf of them.

The Healing Process

When you cut a coral, you leave an open wound and a stressed animal. Healing follows a predictable arc, and knowing it keeps you from panicking or interfering.

In the first days, the frag closes up and looks miserable. This is normal. The coral is sealing the cut and directing energy inward. Over the following one to two weeks, tissue begins to grow over the cut edge — you will see the raw skeleton or wound margin slowly get covered by a thin advancing layer of tissue. Once the wound is sealed, the frag reopens, resumes normal polyp extension, and begins the more visible work of encrusting: spreading its base tissue out onto the plug and gripping it. When you can gently tug the frag and it holds because tissue, not just glue, now anchors it, healing is essentially complete and grow-out has begun.

The conditions that speed healing are the same ones that keep any coral healthy, dialed slightly gentler: stable water, moderate light, and low, non-scouring flow so the wound is not blasted. Cleanliness matters because open tissue invites infection. Above all, leave the frag alone — every time you pick it up to inspect it, you reset the clock and risk tearing fresh tissue.

Encrusting: The Foundation of Growth

Most corals grow by first encrusting — spreading a base of tissue and skeleton outward across the surface they are mounted on — before they build upward or outward into their colony form. An SPS frag encrusts over its plug and onto surrounding rock, then starts branching or plating. An LPS encrusts its base and then adds heads. Understanding this tells you what to look for: the first real sign of a thriving frag is not vertical growth but the base creeping outward onto the plug. Encourage it by mounting frags so the base contacts the plug well, and by keeping the plug clean of algae that would compete for that space.

Growth Rates: Honest Expectations

The most common beginner frustration is expecting a frag to become a colony in weeks. It will not. Coral growth is measured in months and years, and rates vary enormously by class.

• Soft corals are the fastest. Many leathers, GSP, mushrooms, and zoas visibly spread within weeks and can double in a few months under good conditions.
• SPS corals grow surprisingly fast once established and stable — a montipora can plate outward noticeably over a couple of months, and Acropora branches extend visibly over a season — but only when chemistry is rock-steady.
• LPS corals are generally the slowest to multiply heads, often taking many months to add a head or noticeably enlarge, though they compensate by being forgiving.

The universal accelerant is stability, not any additive. A frag in a tank with steady parameters, good light, and appropriate flow grows; the same frag in a swinging tank stalls. Feeding accelerates the corals that eat, as the feeding chapter covered, but stability underlies all of it. Do not chase growth with supplements; chase it with consistency.

The Grow-Out Rack

The engine of serious propagation is a grow-out rack — a dedicated area, often an egg-crate or acrylic frag rack, where frags heal and grow in controlled conditions before being placed, traded, or sold. A grow-out rack gives you a low-flow, moderate-light nursery zone, keeps frags off the main rock where they would be hard to retrieve, and lets you watch each frag's progress at a glance.

Mount healed frags on the rack in the light and flow appropriate to their class — the rack does not have to sit in one uniform zone, and many keepers position racks so the top rows get more light for SPS and the lower rows less for softies and LPS. Because grow-out is often about volume, a capable full-spectrum reef LED over the rack area ensures even the frags you are growing for trade or sale get the light they need to color up and grow, not just survive. Keep the rack clean, because algae on plugs competes with encrusting coral, and a quick pass with the same tools from your coral fragging kit lets you re-glue any frag that pops loose and trim any that overgrow their neighbors on the rack.

Compounding: The Quiet Math

Here is the part that makes propagation addictive. A single frag, grown out, becomes a colony. That colony can be fragged into several frags. Each of those grows into a colony. The math compounds, slowly at first and then remarkably, until a single coral you bought once has become a dozen you can keep, trade, or sell. A modest grow-out rack running for a year quietly turns a handful of starter frags into a collection worth many times what you paid. This is how experienced reefers fund the tank tax — not by any clever trick, but by patience and compounding, the same forces that run everything else in this hobby. Scaling that into a real trading operation is the subject of the final chapter.

Reading a Struggling Frag

Not every frag thrives, and reading a struggling one saves it. A frag that stays closed for weeks, fails to encrust, or shows tissue receding rather than advancing is telling you something is wrong: usually flow that is too strong, light that is wrong for its class, an unstable parameter, or an infection at the wound. Work through those in order. A frag that browns out needs more light or lower nutrients; one that bleaches needs less light or more stability; one that is being nipped needs the culprit found. Most struggling frags recover once the single limiting factor is corrected — the trick is changing one thing at a time and giving it a week before judging.

Patience Through the Ugly Phase

Every fresh frag goes through an ugly phase, and the keepers who lose frags are usually the ones who could not leave them alone through it. For the first days to weeks a frag looks worse than the coral it came from: closed, dull, maybe slightly receded at the cut. This is not failure; it is healing, and healing is not pretty.

The temptation is to intervene — to move the frag to better light, to dose something, to pick it up and inspect the cut. Resist all of it. A healing frag needs stability and to be left undisturbed far more than it needs any active help. Set it in gentle flow and moderate light, keep the water steady, and check it with your eyes, not your hands. Given a couple of weeks of being ignored, the great majority of frags reopen, seal their wounds, and begin to encrust. Doing nothing, correctly, is the whole skill.

FAQ

How long do coral frags take to grow?

It depends heavily on the coral. Soft corals like leathers and zoas can visibly spread within weeks. SPS such as montipora and Acropora grow noticeably over a couple of months once conditions are stable. LPS are usually slowest, often taking many months to add heads. Across all of them, stability matters more than any supplement — a frag in steady water grows, while the same frag in a swinging tank stalls.

Why is my coral frag not growing?

A stalled frag usually faces one limiting factor: flow that is too strong, light that is wrong for its class, an unstable parameter like swinging alkalinity, or lingering wound stress. Corals also encrust outward across their plug before growing upward, so early progress is easy to miss. Confirm stability, place the frag in appropriate light and gentle flow, leave it undisturbed, and change only one variable at a time.

What is a coral grow-out rack for?

A grow-out rack is a dedicated frag nursery — usually egg-crate or acrylic — that holds healing and growing frags in controlled light and flow, off the main rockwork where they would be hard to retrieve. It lets you monitor each frag, keep plugs clean of competing algae, and organize frags by their light needs, making it the practical engine for propagating and eventually trading coral.