I just decided to paint the back glass on all of my aquariums flat back and I absolutely LOVE how all of them turned out. Doesn't require any masking if your careful and keep a wet cloth around. I used Rustoluem oil based paint that comes in the small cans at any hardware store. I got flat black but it truly doesn't matter. I also used a cheap .50 foam brush. I start with a really light coat first, let it dry for 30 minutes than do a regular coat 3 times waiting 30 minutes between coats. You can look through the front to see if you missed any spots. I seriously loved how they all turned out. Also if you decide you don't want it anymore you can always scape it off with a razor but its a little labor intensive.