Palytoxin???

Well, both. It is concentrated in the mucus of zoanthids, so it is both on the coral and continuously shed into the water. It isn't so much a concern for the corals as it is for your own safety. This is the second most potent non-proteinaceous toxin known--in the worst case scenario, it can kill you by shutting down function at the cellular level. It causes severe tissue death (necrosis), especially if it gets in a cut, etc. If you have zoanthids, please wear gloves.

Also please use a bucket that you dedicate to your s.w. tank. I wouldn't use for anything else ever just to avoid any cross contamination.