the way your discus is peppering up. i dont think it will go away if you change the surroundings. pigeons have peppering. as other stated if they surrounding is too dark peppering will occur. unless it has good genetics. the brighter and vibrant the tank is...the nicer the discus will be. the darker it is the more dark your discus will be. unless you get albino's then it doesnt matter. and i think this applies to all sorts of non albino discus. they will either show peppering, dark edges or stress bars under dark environments unless it has good genetics and are albino's.