Yes, all you really need is live rock. I have some bio bale in my system that Im slowly getting rid of. From my experience, once a tank is cycled and has a decent amount of live rock, Ive never seen the bio load really go beyond the limit where you start seeing ammonia and nitrites. Nitrates on the other hand is often what people have trouble with.
If you dont want too much live rock in the main tank, since it gives more hiding places for the octo, you can keep it in the sump.
If you use bio balls/bio bale, it can clog and build up detritus like sponges do. Although the the bacteria on it converts all ammonia to nitrite and then nitrate, you will have high nitrates. Bio balls will not get rid of nitrates, because you require anaerobic bacteria to that. So to prevent this, you will need to rinse your bio balls every now and then. Just shaking them in salt water will work. Do not use fresh water. Also, since this will kill of some of the bacteria, do not do this to all of your bio balls at once. Do a portion at a time like 25%. When you do water changes, you can use the old water to rinse them.