How to frag corals: SPS, LPS, and soft coral fragging guide

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Why fragging works

Corals are colonies of many genetically identical polyps, so a piece cut from a healthy colony keeps living and can grow into a new colony of the same genotype. In the wild this happens naturally: branching corals broken by storms often reattach and regrow, and in many species fragmentation is a major way the coral spreads across a reef (Highsmith 1982).

Reef restoration uses the same biology at scale. "Coral gardening" grows small fragments in nurseries, then plants them on degraded reefs (Rinkevich 2006). Researchers have also found that cutting slow-growing corals into very small "microfragments" can make them grow faster as tissue spreads out over a surface (Schlecker et al. 2022). Our article on coral restoration and microfragmentation covers that research.

For reefers, fragging means trading or sharing corals, recovering a piece from a colony that is dying back, and keeping a fast grower from shading or stinging its neighbors. Buying tank-raised frags instead of wild-collected colonies also reduces pressure on wild reefs.

Fragging tools

• Bone cutters or side cutters for branching SPS and thin plates.
• A scalpel or sharp single-use blade for soft corals, mushrooms, and zoanthids.
• A coral band saw or fine hand saw (optional) for thick LPS skeletons and encrusting colonies on rock. A saw throws spray, so wear eye protection.
• Frag plugs, discs, or rubble to mount frags on, plus a frag rack to hold them.
• Cyanoacrylate gel (super glue gel) and two-part epoxy putty.
• Gloves, eye protection, paper towels, and a tub of tank water to work in.
• Optional: a coral dip for frags coming from another tank, and rubber bands or toothpicks for soft corals.

Before you cut

• Check the coral is healthy: full color, polyps extending, no receding tissue. Never frag a pale, bleaching, or recently moved coral to "save" a healthy part unless the colony is already dying back.
• Check the water: stable alkalinity, calcium, magnesium, salinity, and temperature for at least a couple of weeks. Cuts heal slowly in unstable water. See alkalinity swings and the reef testing schedule.
• Prepare the plugs first: dry the plug tops, have glue and putty open, and keep a container of tank water at the same temperature.
• Keep the coral out of water as briefly as you can. Many SPS and LPS can be cut in a shallow tub of tank water; brief air exposure for gluing is normal.

How to frag SPS corals

Branching SPS (Acropora, branching Montipora, Stylophora, Pocillopora): pick a branch tip about 1–2 inches (2.5–5 cm) long. Cut cleanly with bone cutters as close to the base of the branch as you can. Dab the cut end dry, put a small ring of epoxy putty or gel on the plug, and press the frag in so the skeleton sits firmly. Hold for 20–30 seconds, then return it to the tank.

Plating and encrusting SPS (plating Montipora, encrusting colonies): snap or cut a piece from the outer edge of the plate, where tissue is growing fastest. For encrusting colonies on rock, cut or chip the rock under the tissue rather than peeling tissue off.

Place new SPS frags in moderate light and good flow, a little lower than the mother colony, then move them up over a couple of weeks. Strong flow over the cut helps keep debris and algae from settling on it. Our guide to reef tank flow covers where to put powerheads.

How to frag LPS corals

Branching LPS (frogspawn, hammer, torch, candy cane): each head sits on its own branch. Wait until the coral is retracted (lights off for a while helps), then cut the branch well below the tissue with bone cutters or a saw. Do not cut through the flesh or the mouth of a head.

Solid brain corals and favia-type colonies are harder. Some can be cut with a saw between mouths, but the risk of tissue damage and infection is higher. Many reefers simply let these grow whole. If you do cut one, make every piece have at least one complete mouth and keep the cut edges in very clean, stable water.

LPS can sting neighbors with sweeper tentacles, so give new frags space on the rack. Some LPS, such as torches, should be handled with extra caution because cut tissue in poor conditions can develop rapid tissue loss.

How to frag soft corals, mushrooms, and zoanthids

Leather and toadstool corals: cut a piece of the cap or a side branch with a clean scalpel. Leathers often shrink and produce mucus after cutting; that is normal. Tie the piece to a plug or rubble with a rubber band, skewer it to rubble with a toothpick, or rest it in a cup of rubble until it attaches in a week or two. Glue rarely holds on fresh soft tissue.

Mushroom corals (corallimorphs): cut through the disc from the edge across the mouth into halves or quarters, or cut the foot off the rock. Put the pieces in a mesh-covered cup or a low-flow spot with rubble so they cannot blow away. Each piece usually reattaches and heals into a new mushroom.

Zoanthids and Palythoa: cut a small cluster of polyps from the rock or plug, cutting through the mat between polyps. Glue the base to a plug. Read the safety section below first.

Gorgonians and green star polyps: gorgonians can be cut and the base glued or held into a plug; GSP can be cut out with its mat or left to grow onto a nearby rock or plug.

Glue, epoxy, and frag plugs

• Cyanoacrylate gel sets on contact with water and holds small, light frags well. Choose a plain gel without added fungicides or mildew inhibitors.
• Two-part epoxy putty makes a strong base for heavy frags, branches, and mounting plugs into rock. Knead until it is a single color, then press it into place.
• Gel plus putty: a common combination is a small ring of putty with a drop of gel, so the frag grips instantly and the putty sets underneath.
• Plugs and discs: ceramic or aragonite plugs fit standard frag racks and let you move a frag later without touching it. Rubble works for soft corals and mushrooms.

Keep glue off living tissue. A thin film of glue can whiten underwater. That is cosmetic and the coral will grow over it.

Healing and growing frags out

• Light: start frags slightly lower than the mother colony and raise them gradually. See PAR and reef lighting.
• Flow: moderate, steady flow so mucus and detritus do not settle on the cuts.
• Water: stable alkalinity, calcium, and magnesium, and enough nitrate and phosphate that corals are not starving (see nitrate and phosphate balance).
• Watch for trouble: tissue peeling back from the cut, brown jelly, or white skeleton spreading over a few days. Remove that frag to stop problems spreading, and check your parameters.
• Growth signs: new tissue creeping over the glue line, polyp extension, and new branch tips or new heads.

Grown-out frags can turn into large colonies. Once a colony reaches the glass, shades neighbors, or touches another coral, it is time to frag it again.

Caring for the mother colony

• Take no more than a modest share of a colony at once, so it keeps most of its tissue.
• Leave cut faces clean and in good flow. Stony corals usually cover the wound within days to a couple of weeks.
• Keep feeding and dosing steady. Don't change several parameters during the same week you frag.
• Avoid fragging the same colony again until the earlier cuts have healed and new growth has started.

Fragging safety and zoanthid palytoxin

Zoanthids and Palythoa in the aquarium trade can contain palytoxin, one of the most potent non-protein toxins known. Testing of zoanthids bought in aquarium stores found high palytoxin levels in some Palythoa colonies (Deeds et al. 2011). Hobbyists and shop workers have been sickened by touching zoanthids, getting spray in their eyes, or breathing steam or aerosol. In one Alaska case series, people became ill after boiling or scrubbing zoanthid-covered rock (Hamade et al. 2015). Eye exposure has caused serious corneal injury (Wonneberger et al. 2020).

• Wear gloves and eye protection whenever you cut zoanthids, Palythoa, or any coral with a saw.
• Cut under water where you can, and point cuts away from your face.
• Never boil, steam, pressure-wash, or dry-scrub rock that has or had zoanthids on it. Work in a ventilated area.
• Cover any cuts on your hands, wash hands and tools afterward, and keep children and pets away.
• If you develop symptoms after exposure, such as breathing trouble, fever, muscle pain, a metallic taste, or eye pain, get medical help and say you were exposed to zoanthids or palytoxin. In the US you can call Poison Control at 1-800-222-1222.

Other corals carry their own hazards. Some soft corals release irritating compounds when cut, and fire coral (Millepora) stings skin. Wearing gloves for all coral handling is a good habit.

Common fragging mistakes

• Fragging a stressed coral or fragging during a parameter swing.
• Crushing tissue with dull cutters instead of making a clean cut.
• Gluing soft coral tissue instead of tying or pinning it.
• Putting new frags in full light and strong flow right away.
• Skipping gloves and eye protection with zoanthids or a saw.

FAQ

Is fragging bad for the mother coral? Not if the coral is healthy and you take a modest piece. Fragmentation is a normal way many corals spread on wild reefs, and the cut areas usually heal over within days to a couple of weeks. Avoid fragging a coral that is pale, receding, or recently moved, and keep flow and water chemistry stable while it heals.

What glue do you use to frag corals? Most reefers use cyanoacrylate (super glue) gel, which sets in water, and two-part epoxy putty for larger or heavier pieces. Use plain cyanoacrylate gel without added fungicides. A small dab of gel pressed into a ring of putty combines a quick hold with a strong base.

How long does it take a coral frag to heal? Soft corals and mushrooms usually attach to a plug or rubble in one to three weeks. SPS frags often start encrusting over the plug within one to four weeks, and LPS cut edges can take longer. Look for tissue spreading over the glue line and polyps extending normally.

Can you frag zoanthids safely? Yes, with care. Zoanthids and Palythoa can contain palytoxin, a potent toxin. Wear gloves and eye protection, cut under water, keep cuts away from your face, and never boil, pressure-wash, or dry-scrub rock covered in zoanthids. Wash hands and tools afterward, and get medical help if you have symptoms after exposure.

Should you dip new frags? Dipping frags in a reef-safe coral dip before they go into your display is a common way to reduce the chance of bringing in pests such as flatworms or nudibranchs. It is most useful for frags coming from another tank. Follow the dip's label and rinse afterward.

References

• Highsmith, R.C. (1982). Reproduction by fragmentation in corals. Marine Ecology Progress Series 7: 207–226. doi:10.3354/meps007207
• Rinkevich, B. (2006). The coral gardening concept and the use of underwater nurseries. In: Coral Reef Restoration Handbook, CRC Press, 291–301. doi:10.1201/9781420003796.ch16
• Schlecker, L., Page, C., Matz, M. & Wright, R.M. (2022). Mechanisms and potential immune tradeoffs of accelerated coral growth induced by microfragmentation. PeerJ 10: e13158. doi:10.7717/peerj.13158
• Deeds, J.R., Handy, S.M., White, K.D. & Reimer, J.D. (2011). Palytoxin found in Palythoa sp. zoanthids (Anthozoa, Hexacorallia) sold in the home aquarium trade. PLoS ONE 6: e18235. doi:10.1371/journal.pone.0018235
• Hamade, A.K. et al. (2015). Suspected palytoxin inhalation exposures associated with zoanthid corals in aquarium shops and homes, Alaska, 2012–2014. MMWR 64: 852–855. doi:10.15585/mmwr.mm6431a4
• Wonneberger, W., Claesson, M. & Zetterberg, M. (2020). Corneal perforation due to palytoxin exposure of domestic zoanthid corals. Acta Ophthalmologica 99. doi:10.1111/aos.14594