looks like one of the Palythoa species as it seems that the coenenchyme (the matting at the base of the polyp) is fused to adjacent individuals. If this is the case, please use caution when handling this coral as palythoa produce a virulent neurotoxin (i.e. palytoxin) in their mucus and reproductive organs.
Your fish and other thank inhabitants should be fine. Just ensure that it is not too close to your other corals. If you use a skimmer or activated carbon, this will remove any toxins that are released. Some marine species have seveloped the ability to consume organisms such as this (some wrasses and nudibranchs).