I'm looking into building a large tank with a sump. The tank is 96L x 30W x 28H (350 gallon), 3/4" glass, and the sump is 72L x 24W x 16H (120 gallon). There will be 4 holes drilled for drains and returns, 2 in each corner of the back glass on top. They're going to be for 2" PVC
pipes. I was planning on drilling 3" from the edge of the glass, both top and side, to the edge of the hole.
My question is do I connect a drain and a return on each side? or 2 drains on one side and 2 returns on the other?
Also, does 3" from the side and top sound ok? or should/could it be more/less?