i cant remember off the top of my head. ill have to call the LFS that is delivering it tomorrow to get them
My guess is that it is 48x24x24. that is a standard 120. that being true, I would do with the Regal (Hippo) Tang over Naso. You don't want a fish that will get to be over a foot long and Regal Blue Tang CAN get that big, but it will take them 10 years and most don't reach that size. If you are tang hungry, the Regal Blue is the biggest you can really fit. You could easily go for a yellow tang (don't they are too common), purple tang (as dominick mentioned), atlantic blue (kinda tricky), powder blue (Ich magnet), Achilles tang (best just flushed down the toliet - guaranteed death in your tank but so F*&KING pretty it is worth it just once).
Now then, lets talk for a moment about real fish: Angelfish. The best looking ones are the big ones, Holacanthus and Pomacanthus families. Most need at least a 6 foot in length tank for the extra swimming room. BUT the Blue Ring angelfish stays nicely in a 120 as will a King Angel (Passar), Majestic (Navarchus), Yellowbar and Regal Angelfish (if you can find a Red Sea variety that is eating - GET IT). These fish are remarkable and can be kept with most soft corals (except for xenia and zoanthids). Leathers, mushrooms, GSP, YSP, nems, nepthia, sinularia, etc can all be kept with the angels and you can have your reef WITH KICK-ASS FISH.
Yes, it is true, I am trying to convert another disciple to my way of reefing, sue me
-Doc