white spots on royal pleco

I have had my royal pleco for a few days now and there are white spots on it. They look a little like ich but none of my other fish have gotten it. A lot of my other fish are real succeptable to ich so I would have thought that it woulda spread by now. is that just part of his markings or whats the deal. I think I may run the diatom just in case, but will that physically take the ich off of the fish I have never used it before and am actually quite confused as to how to get it started (very complicated)

I dont know how to tell the L number. Is there a place where I can look it up. I am running my diatom right now it should be cleared up as soon as the ich begins the cyst cycle and falls off of the fish.

I have an L190 it appears