is it possible to cut tempered glass???

No you cant cut tempered glass- but 20s are not normally tempered.

The problem you will have is with the frame and top.

Buy a bigger tank will be easier, faster and likely cheaper.
 
Nope, no cutting of tempered glass. The glass is under tremendous pressure and any cracking or grinding will lead to failure either when cutting or soon after any pressure is exerted on the glass.
 
but wouldn't you just be cutting out the silicon not the glass?
 
I busted a 4x8 sheet once. I thought I could use a $100 glass cutting bit to do the trick. The entire thing shattered and it took me 2 hours to clean the mess.
 
I worked as a glaziers assistant for a while in my younger years. We were replacing some windows in a condominium in Destin, Fl. These were high-dollar, penthouse condos mind you. I blew out 3 6'x9' 1/4" double insulated storm windows.

Needless to say those aren't cheap windows and made a real mess to clean up.
 
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