The back of my 55 gallon FW tank was marred by calcium deposits (Houston has very hard water), and I tried everything I could to remove them. The spots are on the outside so they are very visible no matter what type of background I used. I tried to remove them with vinegar, no luck. Then I tried CLR and Lime Away - Yeah I know it could have been a disaster, but I was extremely cautious. I had no luck with those products either. I tried a razor blade, but that didn't have any effect. So, I came up with a GREAT idea! I went to Lowes and bought a piece of darkly tinted plexiglass and had it cut to the dimensions of my tank. The plan was to slip it INSIDE the tank against the back wall. It would have been a great plan except that there is this pesky bar dividing the top of the tank. The Plexiglass wouldn't fit! In all of my wisdom, I decided that the bar couldn't possibly serve any useful purpose, so I made a small cut, to allow the plexiglass in. The instant I cut through the bar, the tank bowed almost an inch front to back!! I slipped the plexiglass in and locked the front and back of the tank together using a caulking gun turned upside down! I have since screwed the plastic bar back together using a metal strip and about 10 screws. Do y'all think that the glass might be damaged? Will this hold?