Will this work?

[wackyzman]

I have a 90G Glass tank that is drilled for a sump. I do not plan on ever using this tank with a sump. I know I can go get so bulkheads and cap them off, but that will mean that I will have to drill holes in my cabinet to make room for the bulkheads sticking out the bottom of the tank. So, with that being said, could I use square pieces of glass (same thickness as tank) and put them over the holes and seal them? Thanks.

[chbix]

You could...but that's one hell of a point of failure. Do you want to risk it all draining?

I'd consider buying or trading for a new tank that isn't drilled!

[dmolavi]

What chbix said. You're looking at probably 700lbs of water weight in the tank, plus your substrate. That's a lot of pressure on that area, definitely the weakest point. 90 gallons is a lot of water to find on the floor...

[Fishfur]

If you could arrange for the entire bottom of the tank to be supported right on on the glass, not just the rim, and you used a patch as large as practically possible, you might get away with it.

A patch as wide as the tank, less an inch on each side, and at least that long.. a big square. Silicone between patch and tank spread as evenly as you can, pressed down evenly and well stuck on, then sealed all around the edges to prevent any chance of catching or cutting yourself when you work with the tank.

If you had a thick piece of plywood underneath the entire base that was well supported itself, it would spread the pressure, and the big patch also would spread the pressure.

But is it worth the risk that it might fail, which is the key thing here ? If it were me I would not do it.