help with plumbing

[m000240]

I am about to drill out my 75 gallon rectangular tank. I would like to run two internal overflow boxes, with one drain and one return each. The question I have is how much linear overflow space should I have? (right now I have 12" on each overflow for a total of 24") and what size drain and return pipe should I use? (I was thinking 1" pipe each way) I am going to start small as far as livestock, but as I become more experienced I don't want to be wishing I'd added an extra (or larger) overflow. Any suggestions would be helpful, thanks!!!!
Alex
Honolulu, HI

 

[fishtk75]

As I was told always go bigger on returns lines 1" out = 2" to 21/2" in so pump has enough more water water coming in and not starving the pump or too much in flood over the top.
I have one over flow a 11/2" in and 3/4" out on my 75 gal tank that is prdrilled from factory for 600 gph and I have a 9.5 mag on it.
I saw other ones on pics have it half way down the sides.
I drilled and put in a 11/2 return for my refuge so it has even flow making sure it will not go over the top.
hope it helps.