[reddhaus]

I am going to be using a 20gal high for a refugium for my 125 gal reef tank. The refugium will be sutup under the display tank and will overflow into my sump. I planned on using a small mag pump to pump the water from my sump over to the refugium. I don't know what size pump to buy as i do not know what the optimal flow rate is for this size refugium.

Can anyone give me some ideas or suggestions. Is there some sort of basic rule of thumb for determining this.

Any feedback would help greatly. Thank You.

[dattack]

Woudln't it be easier to T-off the overflow pipe to drain into the refugium? Saves you money on buying another pump.

Some people recommend 2x-5x the size of your refugium. From my experience, it really doesn't matter. I prefer fast flow through the refugium because when it gets too slow, the water becomes stagnant at different places in the refugium and I see more unwanted algae growth.
I think so long as the flow through the refugium isn't too stagnant or isn't too fast like a whirlpool where everything gets tossed around (especially the sand bed), then you will be fine.