mojo
Aquarium Advice Apprentice
In both books listed above (I read'em), undergravel filters are considered "old school" and not of benefit for modern reef aquariums. As darb2 said, they tend to trap detritus and require a lot of maintenance to keep clear. As you continue to learn and read, you'll find that there are plenty of other things to do in reefing without having to bother with the UGF, so if I were you, I would abandon that as an option of filtration.