[davocean]

It depends on what your purpose is for running a refugium.
The name itself, taken from the word refuge, it's original intended use is for a place lacking predation for the intended purpose of allowing pods a safe zone in order to reproduce.
So if you have fish that eat pods such as mandarin's that must have them, or anthias or anything else that greatly benefits from always having that live natural food source available, they are awesome.
Also having a reverse light cycle on one helps stabilize PH drop at night.
If you are looking for nutrient export, it could depend on size of fuge and your setup as to whether or not that does much for you.
You do not need sand to have a beneficial refugium, I never have sand in my fuge.