thanks paul28. i think im going to take out my bioballs and use live rock rubble. but how big should they be? marble sized? or what?and the way my tank is built(its an old terracore) the filtration system is build in the back of the tank, it is the whole lenght/heigth of my tank also, it goes all the way alongside the back of my tankm and its about 3 inches wide. now my other question, there are slits in the filteration system and in the middle is about a 24 in space were my bioballs are. if i take my bio's out and put in live rock, it will be 18in. at the very bottom. would that still be ok to use? or does it have to flow past it?

please post an answer i really need one

thanks much guys