What are the dimentions of the tank? because I know they say a volitan can live in a 50, but I personaly feel they are to small... the volitans can get as big as a basket ball, so they need a taller tank then most 50gals offer I have seen more then one adult volitan swiming around with his fins out of the water, wile almost touching the sand at the bottom. If you aren't set on a volitan I would recomend a slightely smaller lion but just as impressive, the radiata lion
http://www.liveaquaria.com/product/prod_display.cfm?c=15+36+241&pcatid=241
Equipment, you will want a skimmer, you will want some sort of flow mechanism (pumps and/or powerheads) for 10x volume flow an hour so around 550gph, you will want biofiltration (live rock, sand, biomedia in a sump etc), a sump is always a good idea with preds, basic lighting so you can see your fish haha, heater... that basicaly covers it... feel free to ask more.