A coral frag is a small fragment of a coral colony which is usually glued to a frag plug. Corals are fragmented in the reefing hobby in order to sell and trade smaller pieces of a coral.
Due to it´s size coral frags are very popular. Reef hobbyists are getting an exact clone of a mother colony at an affordable price. Another reason of the popularity of coral frags is that a lot of hobbyist enjoy to grow out smaller frags to a colony on their own rather than just placing a large specimen in their tank right from the start.
If you consider fragging your coral you should consider to start with your SPS stony corals. Even if SPS are usually harder to keep in the tank, fragging of SPS is much easier than e.g. LPS stony coral.
In order to frag SPS you usually just need a side or bone cutter, a small bucket of water, some glue and some frag plugs. I recommend cutting your SPS from the bottom so that you get a bigger piece first. This larger specimen can than be cut to smaller coral frags based on the desired size. This way you get a nice growth form for your frags.
Before you start to glue your frags on the plug you should make sure that your frag has a smooth surface. Put a very small drop of the glue on the plug and press the frag onto the plug for approximately 10 seconds. Your frag should sit tight by now and can go back into the water bucket. In order for the frag to heal we recommend to put some drops of iodine into the salt water.
If you plan to frag LPS stony coral you should make sure that you have the right tools which ideally would be a diamond band saw or alternatively a Dremel tool with a diamond blade. When you cut LPS coral you should make sure that you make a clean cut and hurt as little as possible of the coral polyps tissue. This way you make sure that the coral is able to recover from the cut and can grow out to a new colony.
In any case you should always make sure that your coral frags have time to recover. A usual period for a frag to recover is two weeks. At this point SPS frags should start to encrust on the plug which is a good sign of strength and health. At this point you can start to sell your frags and make other reef hobbyits enjoy the mini-clones of your beloved coral colonies.