I have a friend who is setting up a new saltwater tank, and we've recently been discussing the benefits of live rock, and even made some. It's the most porous rock I've ever seen, looks solid but you can put a hose up to it most of the way on and water just flows right though it. Would it be possible to set up some sort of freshwater analog? I think the hardest part would be coming up with a sample of whatever micro and macro life lives in the environment you are trying to recreate in your tank to seed the rock with. What does everyone think?