I have an Innovative marine tank and the back wall is actually a black acrylic insert. I dont scrap it cause Im afraid that scratches would really show and be an eye sore. I do ocassionally wipe it with a soft cloth (actually a lap sponge, I get from working in surgery) when I do water changes. I hope it turns purple eventually. Or I'd be okay attaching GSP to it but I dont want to glue it.