A refugium is basically a sump, so you could put it under your main tank saving you space. then throw some sand, LR rubble, and macro algae in it. Refugiums are beneficial because:
Decreased Nitrates
Decreased Phosphates (bad algae food)
If you run your refugium lights on a reverse timer it helps to stabalize your pH
Provides a "Refuge" for many amphipods and copepods

Many beneficial factors are associated with a fuge, definatly a good idea.