UG filters trap waste over time and if your using a sand bed I dont even think you can use a UG filter. The sand will fall right through the filter and plug it.
Live rock at least 1 pound per gal
. Live sand or a good play sand that is safe for aquariums.
Do a google search on skimmers and you will see what were talking about.
Or superskimmer.com has some nice units.. I run the reef devil on both my tanks.
Did you mention what size tank?
Power heads can be used for added flow in a tank.
You also need to think about lighting and what animals you want to keep. There is a lot of work that goes inot setting up a SW
tank, its not like a FW
tank that can be set up in a few hours.
Keep doing you research and you will be fine..