drilling limits

[mr_alberta]

I have 7 holes drilled in my tank. 3 holes are 1.75", 2 holes are 3" and 1 hole is 2.5". The glass is 1/2"

You don't have to drill holes if you don't want. You could always use u-tubes and have siphons on your pumps.

[mark]

In the bottom of mine there's 3x3" and 5x1.75" holes. Panel's 69x20" 1/2" thick.

Can't find the reference, but diameter of hole, between edge and hole okay (the edge of my 3" diameter holes are 3" from the outside edge of the panel, tank was built by Bow Valley Aquariums).