Back into it after 15 years

[azsoccerpop]

I recently purchased a disassembled used 90 gallon OceanVu acrylic reef tank with a HUGE builtin overflow. the overflow box is 18" x 7" and sits juts off center. The tank is bottom drilled for the feed a a sump I have to purchased and was also bottom drilled for the return which is a ball valved flex pipe. The overflow was also drilled about 6" from the bottom and had a and then on either side about 3" from the top with one of the sides having a flex pipe return to the tank. I assume that water spilling into the overflow is the primary method that feeds the sump and that theflex pipe from the overflow into the tank was a return just like the bottom drilled. I don't understand the 6" bootm drill unless that ciuld have been used for a skimmer sitting directly in the overflow? If any has any ideas? I cant beleive it was just meant for the tank to dump into the overflow otherwise the top skim would likely do bery little or I would have to turn the tank over really quickly to keep up? worse if the pump shut off the tank would dump all the way to the bottom? if pictures or more info would help please let me know. Thanks for reading my post :worried2:

[Pandagobyguy]

This is personally what has helped me understand the ins and outs of plumbing. If you have two pre drilled bottom holes then it is probably wisest to do a bean animal overflow.
Post a pic of the flexible tubing???
It could be designed as a return (should be if it is flex tube).
As far as the spilling into the sump goes. You should design your system so that if power cuts out it will not overflow the sump.
For example in my tank every inch of depth is 3.1 ish gallons.
I set my overflow wall at about three inches below the top of the tank (a little lower actually because i probably wont have the tank totally filled).
My sump is 20g filled halfway so i know that if the power goes off the sump should fill completely and not overflow.

All of that said i am relatively new myself so (as with all things reef) id reccomend second opinions and research.

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[azsoccerpop]

Thank you. I am hoping that the original local Arizona manufacturer oceanvu is still available or can be contacted tyo help me understand if this was modified or original design