Maybe because of the fact that there are MANY different white spots and films that could be affecting him. You were VERY vague in your description so what Orion asked was for more info on WHAT the spots and coating looked like. Your lucky she didn't ask you for tank size, water parameters, tankmates, foods, etc which would normally be asked. You failed to give us more info than a clownfish lights off spots and coat lights on 12 hours gone. That will not get you answers. I would be willing to guess the coating is excess slime production maybe because you have a nocturnal predator or something is wrong with the lighting, or there is some kind of disease it is fighting and you can only see it when the lights go off. If you stick with this attitude NO one will give you responses. Orion did not ask anything out of the ordinary and she actually forgot a lot of questions, so don't go blaming anyone except for yourself for not giving more information. Had you given all the info that has been mentioned in the above posts you would more than likely of had a person respond correctly the first time. Anyway, hope this helps.