Using hammer and chisel we drill (hammer) holes into dead coral substrate. This is extremely arduous as the substrate is rock hard. The corals would then be inserted into the hole and we would use bamboo chopsticks to wedge the corals into place. The advantage of using bamboo chopsticks, is that eventually they would disintegrate leaving just the coral fragment which will have fused to the substrate by then. The disadvantage was that it was very difficult to ensure all the fragments had been firmly fixed in place and many would be lost.
This technique has had varied success and is largely affected by the skill of the diver carrying out the task. If the standing dead coral was too loose, or brittle then it could tumble and be washed away, so selecting a suitable piece of dead coral is important. Also there could be organisms on the standing dead coral that could affect the health of the fragment. Sometimes we discovered that the fragments were covered in sediment, due to the seasonal rise in the level of the sand and the fragment having been attached too close to the sand. However, if the correct type of substrate is selected and the fragment is attached high enough from the sand we can see this is effective and we have many healthy coral colonies.
Fragments are cemented to breeze blocks on the dive boat and then put into place underwater. This has shown good results and many of our test subjects are healthy and growing well. As the breeze blocks have no organisms growing on them, prior to attachment
, this is one factor less for the coral fragments to deal with. Eventually the breeze blocks will provide a habitat for other coral species to naturally settle onto. However, the breeze blocks are heavy and impracticable if you are trying to rehabilitate a large area.
By far, the highest success rate has been attaching the fragments to metal frames. The frames are manufactured so that the coral can be attached about 8″ above the sand, which avoids sedimentation. The frames are also free of aggressive organism that would affect the coral. Another great advantage is with the monitoring. When attaching corals to the natural substrate it is difficult to track where and how many corals are surviving. However each rack has a certain number of fragments attached so it is very simple to assess how many have survived.