[fatman]

I use glass-holes for the vast majority of my tanks, with a Calfo over flow if the tank is a custom made tank without European bracing or plastic trim. I always use two bulkheads in my overflows with each sized large enough to handle the entire flow needed. This provides redundancy against one bulk head being blocked as well as making the overflows virtually noise free. If possible always feed your skimmer from the overflow directly. If using a HOB skimmer, hang it where it gets its water from its own little compartment and run the overflow directly into that compartment and let it overflow into the excess water into the sump, This will insure the skimmer gets straight raw water skimmed from the display tanks surface. Be sure to flow the water from the skimmer into the sump not the skimmer feed compartment.