From what I have understood, bio-balls, bio-wheels feed nitrates back into the system causing algea issues to develop.
If you are doing a reef tank, my recommendation is to go with live sand and live rock as you main filtering medium. Add a good skimmer. Use a sump/refugium setup and all should work well for you.
I have been here for just over a year and started with a HOB filter and a skimmer/live rock and the the such. Since then I have upgraded lighting, added a sump, and now building a refugium to add into my system in a few days...
From what I've been told, the bio balls are a big no no in a reef setup as they can harbor nitrates as others have stated. I was using the bio balls and have not been able to get my nitrates below 10. Normally they stick at 20.
I've just finished removing all my bio balls and have replaced them with LR.
If you're going to do this, just make sure that if your tank is done cycling, that the live rock is cured. If not, you're probably going to get another small cycle...amonia spike. Some Amqeul should handle that. If it's still cycling, you won't need to worry about that.