Brett,
This is a great question to ask before taking the steps into incorporating a refugium into your system. Especially when your system is already established.
The biggest desicion to consider with refugiums when you are going to use one is
what kind of refugium will it be. There are basically two different kinds of refugiums that you can use.
1) The DSB (DEEP SAND BED) Refugium, this refugium will house ~4" of sand or mud of some kind, some live rock (1 to 1.5 Lbs. per gallon of water volume), and some kind of macro algae (calurpa, cheato, or otherwise).
- I used this style refugium for my 105, and i used this product.
http://www.caribsea.com/itempage_refugereactor_theark.htm
2) The BB (BARE BOTTOM) Refugium. This style of refugium is all about the same as above, without the sand. without the sand however you will not be able to "root" any macro algae or mangroves except for on your L.R. So in this case it would be advantageous to include a separate area for your Mangroves, or create a small rack out of some egg crate to secure them in.
Both of these methods have there merits, both of these methods have their faults. It is truly up to YOU and your personal opinion of how you would like to maintain this area of your system.
You will do good to light the refugium with around a 6500K light (LED will work too).
I hope this has helped you at least a little.:jester: