Hi andycook:
I think that your idea for rubble sizing is right on. I think it is driven as much by aesthetics as it would be for maintenance. What I have found with my system is that the rock is rather loosely placed on the bottom, so there are really no areas that accumulate detritus. Essentially, the rubble bottom that I am using is a bare-bottom system, I suppose. Hence my thoughts about running lots of flow in the system.
The UGF ideas that have been proposed in this forum sound fantastic. I'd love to see what kinds of things reefers are doing along those lines!
I found that it is quite easy to get realtively inexpensive slab rock and "bust it up" with a soft mallet to meet your own size requirements.
Last night, I was at the house of a local reefer/friend who has a rubble bottom similar to mine in his 350gal, and the tank/effect is stunning. He has all kinds of Zooanthids, Blastomussa, Faviids, etc throughout his rubble bottom, and the sheer diversity of life is amazing!
He has a very large population of foraging fishes, like Mandarins, blennies, gobies, Centropyge Angels, Leopard Wrasses, etc. All are thriving, and the colors are spectacular.
Again, I think that the "rubble bottom" idea is really a neat concept. Hardly rocket science, but just another way to run a cool reef tank!
If I had to do it all over again, I think that I would have ran my system "fishless" for a few months, while innoculating the system with cultures of amphipods from a source like IPSF, and really letting the system acheive maximum biological diversity before stocking with fish and corals...Would take a lot of patience- but how cool would that be?
Scott