Sorry about not getting back to you on your biodiversity question
@Erin O . However, you already received many good answers. I will only add that, personally, I would not start a new system without live rock. I could go on about this but presently lack the time to do so. Also, if you have the ability to add live rock from different systems it will help with biodiverseness. Hey, maybe if you ask very nicely, you can talk a few members into sending you a piece or two of live rock from their systems!