i agree ruaround. i don't have a dsb. you don't even have to have substrate at all. i would recommend against it though(the ugf), because it can collect debris and become a problem later, and you don't want to tear your tank up after a year or so because of the ugf, when it's really unnecessary. but, your tank, your choice. just realize there are countless options at hand, and the best advice is do some research and know what your long term goals are and plan the tank around that (if you have the luxury of doing so). anyway, to answer your q:
1)a refugium is a [tank or otherwise] that you set up for the purpose of having [plants or animals] that you need to keep separate from your main tank for whatever reason. totally optional. differs from a sump because it usually requires some sort of lighting.imo
2)a protein skimmer is a fiter that uses concentrated micro air bubbles forced up a tube that separates the proteins and other compounds from the water to be removed in a collection cup. helps for a cleaner system, very nice to have, but not 100% necessary either.
with a reef tank, you want adequate lighting, circulation, and filtration (in all necessary forms). this will all add to good water quality which is essential for reef tanks to survive. imo
hope this helps-welcome to the board
=)
