How to Frag and Clone Coral Safely in a Reef Aquarium

Updated 5 November 2026 · Standard formula, shown below

Fragmentation, or fragging, is the process of cutting a piece from a healthy coral colony and reattaching it to a new surface, where it grows into a genetically identical clone. This guide covers the essential steps for fragging both soft and small-polyp stony (SPS) corals, the tools you need, and how to do it with minimal stress to the parent colony and the new frag.

What You’ll Need

Coral cutting tools: bone cutters, coral scissors, or a razor blade (depending on coral type)
Frag plugs or frag discs (ceramic or plastic)
Coral glue (cyanoacrylate gel) or epoxy putty
Rubber bands or fishing line (for some soft corals)
Small container with tank water for holding frags
Disposable gloves and safety glasses
Iodine-based dip (optional, for disinfecting cuts)
Clean, sharp cutting surface

Step-by-Step

Prepare your workspace. Clean your cutting tools with a 10% bleach solution or isopropyl alcohol, then rinse thoroughly with fresh water. Set up a small container filled with water from your display tank to hold the frags.
Choose a healthy parent colony. Only frag corals that are fully extended, brightly colored, and free of pests or disease. Fragging a stressed colony can cause it to decline further.
Remove the parent colony from the tank. Gently lift the rock or frag plug it’s attached to and place it in a shallow container with tank water. Keep it submerged as much as possible during cutting.
Make the cut. For soft corals like zoanthids or mushrooms, use a razor blade to slice through the base or stalk. For SPS corals, use bone cutters to snap off a branch tip (1-2 cm long). For LPS corals, use a saw or cutters to divide the skeleton. Always cut cleanly and avoid crushing the tissue.
Rinse the frag. Dip the cut piece in the tank water container to remove any loose tissue or debris. If you have an iodine dip, follow the instructions to disinfect the frag before mounting.
Mount the frag. Apply a small drop of coral glue to the frag plug or disc. Press the frag onto the glue and hold it for 10-15 seconds until the glue sets. For soft corals, you can also use a rubber band or fishing line to hold them in place until they attach naturally.
Place the frag in the tank. Put the mounted frag in a low-flow, low-light area of your tank to acclimate. Over 2-3 days, gradually move it to its final location with appropriate lighting and flow.
Return the parent colony. Place the parent back in its original spot. It may take a few days to fully recover and reopen.

Common Mistakes

Fragging a coral that is already stressed or diseased.
Using dull tools that crush tissue instead of cutting cleanly.
Cutting too large a piece from a small colony, which can weaken it.
Placing the frag directly into high light and flow immediately, causing shock.
Not disinfecting tools between different coral colonies, spreading disease.

Tips

Start with hardy soft corals like green star polyps or zoanthids before attempting SPS.
Make multiple small frags rather than one large one to reduce stress on the parent.
Keep the frag in a quarantine tank for observation if you have other corals.
Use a frag rack to keep new frags off the sand bed and in stable conditions.
Ensure your water parameters (alkalinity, calcium, magnesium) are stable before and after fragging.

Troubleshooting

Frag is not attaching to the plug: If the glue doesn’t hold, try using more glue or an epoxy putty to create a larger base. For soft corals, use a rubber band or a needle and thread to secure them temporarily.

Frag shows tissue necrosis (white or brown spots): This can be a bacterial infection. Remove the frag from the tank and dip it in an iodine solution (follow the product instructions). If the necrosis spreads, discard the frag to protect your other corals.

Parent colony is not opening after fragging: Give it time and ensure it’s in a low-stress environment. Check water parameters and consider moving it to a slightly shaded area for a few days.

Frag is being knocked over by flow: Use a heavier frag plug or secure the frag with epoxy putty to a rock. You can also place the frag in a lower-flow area until it attaches.

Algae grows on the cut edge: This is common and usually harmless. Gently scrub the area with a soft toothbrush during a water change, and ensure your nutrient levels are not too high.

Frequently Asked Questions

How long does it take for a frag to attach to the plug?

Most corals will attach within 1-2 weeks. Soft corals may attach within a few days, while SPS corals can take longer. You’ll know it’s attached when the tissue grows over the glue and onto the plug.

Can I frag any coral?

Most corals can be fragged, but some (like gorgonians) are more difficult and have specific requirements. Start with easy corals and research the specific type you want to frag.

Will fragging hurt the coral?

Fragging causes stress, but when done correctly, healthy corals recover quickly and the cut heals. The process mimics natural fragmentation that occurs in the wild.

How many frags can I take from one colony?

It’s best to take no more than 10-20% of a colony at one time. For SPS, one or two branch tips is usually safe. Let the parent recover fully before fragging again.

Do I need to feed the frags?

Most corals get energy from light and photosynthesis. However, some LPS corals benefit from occasional feeding of small pieces of food like mysis shrimp. Start feeding after the frag has attached.

Can I sell or trade frags?

Yes, fragging is a common way to propagate corals and share them with other hobbyists. Ensure you only trade healthy, pest-free frags.

Method: the standard formula for this calculation, rounded as each result states. See how the calculators work or report an error.