Pretty neat. I had not seen that before. Should act like artificial live rock, with better surface area. The advantage of that stuff over bio-balls, would be the surface area within the block, as you had mentioned. Bio-balls only host aerobic bacteria. No areas of low oxygen. The block would host aerobic bacteria on the outer surfaces, but would also host anaerobic bacteria inside, like live rock would. I might try some of that in the new nano, since I don't plan to have that much live rock in the display either. Wish I hadn't just ordered from BRS earlier this evening.

Thanks for posting that though. I was going to go the rubble rock in the sump route, but this looks like an interesting alternative.