ManWorld42 wrote:

I was looking at some at my local Home Depot. The rocks seem very
porous and probably can support quite a good bio filter. Anyone with
experience with these rocks instead of gravel?

I've seen lava rock recommended for this very use. As Netmax noted, the
rock has lots of sharp edges, so it could be tough on any fish that
bumped into it. Used in a sump or instead of bio-balls, though, it
should make a pretty good home for bacteria.


--
Eric Schreiber
www.ericschreiber.com