This is what my refuge looked like a few months after I built it. Although now it houses macro algae and my anemone and clownfish.
As per flow rate, that would depend upon how the refuge is tied into your main tank. My refuge is in a direct line from the main tank and empties into the sump, so its flow is dictated by my sump's pump going into the main tank. For a slower flow, you would have to place the refuge above the main tank and have a seperate pump and overflow to be able to control the flow rate. Of course, any flow rates would depend upon the size of the refuge, but will say there is nothing wrong with a good flow going through it. A slow flow would most likely cause stagnant areas which just allows detritus and cyanobacterias to collect/form.
I have some very good links to articles on as well.
Chuck