Fragmenting a Green Tree Coral

Why Would You Want to Do It?

Some soft corals grow very rapidly and, if unchecked, can begin to poison other corals in the tank with allelopathic toxins. The toxins can work systemically throughout the tank and can be reduced though the use of activated carbon, but are particularly damaging to adjacent corals. This photo shows why it is necessary to use carbon and the importance of occasionally fragmenting a coral. The Anacropora colony to the right of the large tree coral in the center of the photo has already lost a significant patch of live tissue from contact with the green tree coral colony. The blue-tipped Acropora formosa in the background also has some dead branches due to its proximity to the green tree coral. Even part of the Alveopora colony to the left of the green tree coral is partially retracted. I've been propagating this species of green tree coral for about seven years now, and it is particularly well suited to propagation due to its fast healing, quick attachment and growth, and its resistance to disease or infection. The colony in this photo is likely by now a 10th to 15th generation fragment.

Get Your Tools Together

Some of the tools you will need for this procedure are shown in the photo to the right. Most forms of gel superglue work well. The serious fraggers can be identified by the size of their superglue bottles! The plastic toothpicks are available at most drugstores. Any plastic tooth picks can be used. The commonly available ones shown in the photo that I have found in my local drugstores have a "brush" end on them for removing plaque more effectively from teeth; this does not matter much for coral fragmentation purposes, though. They even come in blue and pink in case you want to spice up your "frags" a bit or you are certain of the sex of your coral.

Hack up the Coral

If possible, it's best to remove the coral from the tank so that any toxins that ooze out of the cut tissue will not end up in the display tank's water. The fragments can be cut free with a razor blade as shown, or by using a sharp scissors. Because of the tissue crushing that might occur, some corals can sustain more damage if a scissors is used than if they are cut with a razor blade. Depending upon where the cuts are made, and the nature of the coral species you are cutting, you may need to cut with a sawing motion to get through any of the sclerites (needle-like calcium carbonate internal skeletal elements) you encounter. These sclerites are more numerous toward the base of most corals, and there is less tissue there. This proteinaceous material is the living tissue that will grow and eventually allow the coral to attach to a substrate. Depending upon the coral, if too little tissue is present in the cut fragment, the coral might not heal and attach properly. The size of the fragment may also be important for propagation success. Fragments smaller than two inches long may be difficult to work with and less likely than larger fragments to heal and grow quickly. Until you have experience fragmenting the particular type of coral you are working with, it is best to err on the side of cutting too large a fragment.

The Toothpick Method

Using a rotating motion, pierce the fragments using the toothpick's sharp end, about ½" from the base of the stalk.

Left: piercing the coral near its base with a toothpick. Right: multiple fragments ready to be attached to a base. Multiple cuttings in such a small container can foul quickly, so do not leave them there for long.

Gluing the "Frags" Down

Small pieces of live rock or clean dry rock can be used for mounting. Ideally, the rock should have a small hole or depression that the live coral tissue can protrude into, with good attachment points on either side of the hole for the toothpick. The sections of the toothpick extending from either side of the coral fragment are dried before positioning, and the areas of the rock where the toothpick will be attached must also be dry. If using live rock, quickly drying just the section of rock where the toothpick will be attached will allow most of the encrusting organisms on the rock to survive. The glue can then be applied to the toothpick or the fragment, and the fragment held in place until the glue firms up a bit. It's important that when the gluing down of the fragment is complete, the coral tissue should be just lightly touching the substrate; keep in mind that the coral tissue will likely expand when it is put back into the water. If the tissue is forced against the substrate too hard, it might promote poor healing or disintegration of tissue, possibly by infection. It typically does not matter if the section of tissue that is touching the substrate was the newly cut section. But, strong water flow to cut areas facilitates healing as they are not in contact with the non-native microbial flora that are typically found on substrates.

Once the glue has set up a bit more (10-15 minutes) the fragments can be returned to the tank. The best success rates are likely to occur if the fragmented coral is returned to a tank with conditions similar to those where it was grown. Increased water flow may be important in some cases to help flush away extra mucus and any microbial growths that might take advantage of the damaged coral tissue.

The mother colony is clearly unhappy, but will recover in a matter of days. The spotted goby seems to be questioning the trim job.

Within a few weeks, the fragment will have attached. At this point the toothpick can be removed if you like, or not. The plastic will not degrade, and it typically does not cause any problem imbedded in the coral tissue. The coral will continue to grow, and may eventually encase the toothpick completely. You can remove the toothpick with a rotating motion similar to the way it was inserted. Some corals, though, will adhere strongly to the toothpick, and removing the toothpick might do considerable damage, or might pull the lightly attached coral off the rock. Still other corals seem to "dislike" the toothpick imbedded in their tissues and, while it does not seem to be the source of infections, sometime the coral will attempt to pull all of its tissue away from the toothpick. By this time, however, the coral is usually attached to the substrate and the toothpick is no longer required.

Some Final Notes

The toothpick method will work to varying degrees for many different genera of corals - Sinularia, Lemnalia, Nephthea, Capnella, Sarcophyton, Cladiella and Lobophytum. It tends to work best with corals that have a significant density of sclerites within their tissue. Corals that are less supported by sclerites and are "softer" (e.g., Klyxum or "Colt") can sometimes "melt" away from the toothpick before they have attached to the substrate.

Happy Fragging!

If you have any questions about this article, please visit my author forum on Reef Central.

Reefkeeping Magazine™ Reef Central, LLC-Copyright © 2008

"Frag" of the Month - September 2006 - Fragmenting a Green Tree Coral - Nephthea sp.-