GrotesqueHybrid in a reef tank your live rock is your filtration (also your sand if you have a DSB), A skimmer is also a real good idea. For your sump I wouldnt put any LR or LS in it the LR will just end up being a detritus catcher and usually the waterflow is to fast for sand to sit still. As per Bio balls I would stay away from them. Bio balls only convert ammonia to nitrite and then nitrite to nitrate, from that poin the nitrate goes into your tanks water column, fish can handle it a bit but for corals its a no no. With LR and LS ammonia will be processed down to harmles nitrogen gas, so its a better route.
Save your sump for your skimmer and other equipment like heaters, probes, pumps and other stuff.
Mike