Bio balls

[Rikko]

Hey Corey,

I assume you mean as a biological filter media rather than any other use, right? (Though I bet filter floss would do something interesting in a skimmer too...) If so, I personally think bio balls are a ridiculous waste. They have a good bit of surface area, but really, look at all the air!
Crushed lava rock works great in pond filters and larger FW setups - it would have the same effect in a SW system as far as having a lot of surface area available. My only obvious concern is mineral exchange in a seawater system. I've read a few times that volcanic rock is totally inert, but never saw any decent support for it.

I'm also a pretty big fan of fluidized bed filters - LOTS of available surface area there and it's much more compact.