Bulk Head Question

[intarsiabox]

I assume that 1 1/4" is the ID of the bulkhead? The main purpose of a drain going from the display tank to a sump is just to transport water to a skimmer, refugium, etc., it is not used primarily for tank circulation. I believe the flow rate for 1 1/4" ID pipe is around 750gph and 1" ID pipe is about 600gph. So if you are using a skimmer in the sump you need to ensure that there is adequate flow to feed the skimmer with extra to divert to a refugium or what ever other items you plan on having in the sump. So one drain may be enough. Also remember to size your return pump accordingly, a little bigger is better IMO as you can always throttle the pump discharge down with a valve. Never valve off the intake of a pump.