[kaskiles]

I did what you are saying for my rimless, and used silicone picture frame bumper pads on each corner, which leaves a nice 1-2 mm air gap. Also cut it short in the front to back direction to have a 1 inch gap in back, or 1/2 gap in front and back. I think I found the idea here:

How to Make a Glass Cover for your Rimless Nano Tank — Sunken Gardens

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www.sunkengardens.net

It worked for me, no water dripping off the sides.

 

[kaskiles]

Be careful if you get thick glass cut, it can get heavier than you expect, I matched the glass thickness of my tank and it was way too heavy. Pretty sturdy though...