advice please

[m000240]

So now that I know I can drill my tank, I need some more advice. :help: Specifically how large of holes should I make? I was going to make two internal overflow boxes with 12" of linear overflow each. Each overflow box with one drain and one return. Is 1" sufficient all around? I have heard that the return should be larger than the drain, true? if so, why? I want to make sure I get this right so that later on down the road I'm not wishing I made the holes a different size. Thanks for all your help.
Alex
Honolulu, HI

 

[jasenhicks]

The drain should be larger than the return. Too large of a return will make it difficult for the pump to push the water back. The larger the drain the more water will flow, the return pipe doesnt need to be as big because you have the pump forcing water up it.

 

[acrylic51]

What kind of flow are you after in the tank? This will somewhat dictate what size bulkheads you'd need to use