I'm not sure about octozin, Most people use UV as any chemicals can really throw things for a loop. I think we need to hear a bit more about your tank, especially considering that a marine invert tank would be imune to white spoot as it only affects fish (wich as we know, have vertibrae) How big is it? what fish? how long have you run it? How much LR? Any recent additions? what kind of equipment? what kind of cleanup crew? and cleaner wrasses or cleaner shrimp (Cleaner shrimp really cut white spot down, as infected reef fish seek reprieve from there parasitic problems)?