Haha, yeah their mouth is funny looking. It looks to me like it has evolved to graze algae or some sort from the underneath of rocks from their natural habitats.
As for the scale stripping, I have seen it try it with the Severum in mine, which is why I brought up the Discus, being similar in shape and how they move. It wasn't anything extreme just a couple of little niggles. I would just keep an eye on him incase, sure you dont want anything nasty happening to the Discuss. I think the funniest part is when they graze upside down off bogwood or slate, looks really funny.