Building sump, need help

[zmazza]

Building a 20 gallon tall sump.... I need two pieces of glass for the bubble trap... how wide and tall do they need to be? I'm getting 1/8 double strength glass cut. I don't have the tank, but I'm getting this all done while there's no rush.

20 gallon tall

need 2 glass pieces cut for the bubble trap. What sizes should I get cut?

Thanks!