That explains the confusion. I was thinking of the of the siphon style overflow boxes. Those are the ones that I believe can cause flooding for the reason I had mentioned in my last post. I had never considered notching the glass and building the overflow on the outside.

Glenn

:wink:

Hello,

The total length would be your length of the overflow x1 and your depth x2.

so an 8x5 oveflow would be 18" of actual surface skimming.

But i couldnt say it would be 5" in depth because i was unsure of bracing (cleats and or euro) in your tank...the 8" is a minimum width to fit a 2 1/2" hole(1.5"bulkhead) and a 1 3/4" hole(1" bulkhead) aswell as the street 1.5" 90 that you will use on your durso, aswell as typical flange size.

You/glass company must notch the top, rather than drill holes here, holes will not work.

Marc.

Thanks Marc for all of the information. According to Reef Central's Drain Size Calculator an 18 inch overflow will handle up to 1200 gph which should be enough flow if I decide to make the tank a reef tank later on.