Also, some fish just develop "stress" colors (for lack of a better term.); they are not 3-dimensional like parasites and are just small spots of (usually) darker colors. Don't get hung up on seeing/not seeing white spots; they are not a true indicator of ich in the tank. Different life-stages of ich are still in the tank after the white spots disappear and its vital that the the next batch of free-swimming ich is killed. There are mother cysts in the tank that are not killed by treatment. I'd read the initial posts of the ich stickies, written by Snorvich, at the top of the disease forum. Knowing the life cycle of parasites is vital and will help make sense of treatment procedures.