So the other day when i was at the side of my tank cleaning the back i noticed something a little scary. The front and back panels of glass were bowed out a total of 2 inches
. That's 1 inch (2.54 cm) of flex for each piece of glass. Luckily i had a sheet of 3/4 inch (19.05 mm) marine grade plywood and Thompson water proofing. I had to use a clamp to square up the glass and wooden frame again, screw in a brace, and made a new lid that fit much tighter (that also wouldn't grow a mushroom). I'm almost certain the glass was nearing its breaking point.