Originally Posted by Wy Renegade
Should be roughly 29 1/2" x 11 3/4". You should be able to get a more accurate idea on your own by measuring between the glass panels from the outside of the tank. You should be able to see where the glass panes but up against each other.
That's the estimate I started to use. If I pull the sump, I'll take the inside measure but this number is ringing true to me.
I've always found it curious that the manufacturer's don't post that somewhere but maybe I just drill down deep enough.