here at Thresher Shark Divers on the island of Malapascua just north of Cebu, we seem to have a large number of these Crown of Thrones. I know in small numbers they can help manage the eco system on the reef, but it when they come in their hundreds or even thousands you can clearly see the damage that can be done in a very short space of time. As professional instructors on this wonderful island we dive these sites daily and something needs to be done. we have used several approaches. one was to harvest the Crown of Thorns (COTs) and try and turn them into a compost for the islanders to use. however the smell they give off after was not very pleasant and they took a long time to turn into something usable. we also have the poison guns, this we found to be move effective and less stress placed on these COTs. we go out about once a month and try to keep the numbers under control. It always seems like a losing battle but for a short time it seems to have a benefit for the reef and the nearby waiting fish. on an average outing we will remove in excess of 150 COT per dive.