Starting setup with just a refugium. Some questions.

[dp]

I'm going to set my 125 up to be a refugium. The
actual show tank will be added later next year.
A couple questions I'd appreciate some feedback on. Flow: I am considering putting 2 bulkheads in
the back of the tank and let it flow naturally into the sump just as you would in a 'normal' setup. I'm wondering if the return flow from the
pump in the sump (yet to be determined) would be
enough for the fuge or if I should maybe add an
air pump?
Returns in fuge: What do you all use for the return? spray bar? single outlet?
I'm pretty excited about this!
dp

[Acolin]

The water surface of the vat should be vigorously circulated. Small, simple and inexpensive air pumps are ideal for this task. The sump is the low lying receptacle tank that collects water under the main display tank. Water flow through the vat or sump, should be about five times per hour. In other words, if you add a 55-gallon sump to your 180-gallon display, the water in the sump should turnover about 275-gallons per hour.

If the flow is too slow, cyanobacteria may start to grow in the sump. To remedy this, it may be necessary to add a powerhead to the sump. When the flow rate is too great it may result in tiny air bubbles passing through the sump from the first chamber and consequently being sucked in by the return pump and blown into the main tank. These bubbles can irritate the corals. Additionally, the mud itself may be pushed into uneven piles, which can cause the Caulerpa not to grow.

if the refugium is in the sump, water should flow into the skimmer first. If a hang on the back refugium is up at the display tank level, then its output should go right back into the tank, and the coral’s mouths. A simple return at the water surface is common, since this open mouth can break any possible reverse siphon when the power goes out (do not put the water return deep into the display, unless you drill an air hole at the top).