Ok, so all quick prescriptions aside.. Whatever exactly is the situation? Was that fish in a tank by itself? Is it a new fish?? People! We need information! There is the ultimate cache of fishy experts( I'm not I've but man do I try! I even google stuff!!) here but when in a sure situation a 4 word post will do anything but save your fish..skimmers love details!! Not the saltwater skimmers either!! People skimmers! That skim threads! To save lives!!!!!
What about the other fish with him? Any spots on him?
No the other one is fine, they must of had it at the pet store and it probably broke out as a result of transport stress