WELCOME TO REEF FRONTIERS!!
The best advice I can give you is to find a good book, buy it borrow it or check it out and read it cover to cover.
The best book I have read for people getting into the saltwater hobby is
The Conscientious Marine Aquarist by Robert Fenner
Its a really good book that will cover all the basics.
the second thing to do is find a board like this and ask all the questions you can. Read through posts and use the search function. look at pictures of other peoples tanks to get an idea of what it is you want from your tank.
Are you planning to go reef (live rock fish corals and inverts)
or just fish only?
What will your budget be for this tank? (believe me this can be one of the most limiting factors of what you can do.)
As far as UGFs go, they are pretty outdated and are out of favor with reef keepers. they work well enough, but there are more efficient, mote natural ways to set up a tank.
Powerheads are great for water movement, but they can add some extra heat and tend to look unnatural. Other people prefer to have one large pump with a spray bar attached to create flow. There are other options as well.
Hope this helps
Rachel
