I've just started a 3.3 gallon pico reef and will be updating this section as the tank matures. I'm trying this tank without any kind of filtration other than live rock. I'm currently running a Rio 400 powerhead for circulation and a pair of 5500K 15w compact flourescents. I've started with about 3lb of cured rock and 4.5 lb of uncured Australian reef rock. During the cycling/curing stage of some of my previous tanks, I have observed that many soft corals and mushrooms are far more fit to deal with the ammonia and nitrite spikes than fish (and will remain open while the fish are belly up), particularly in the short term. And as such, I've added some mushrooms and the pollyps that I believe to be hardy. Since the rock is still curing, I am doing very frequent water changes to keep the critters alive. The main method of nutrient export will be the harvesting macro algaes and water changes. The one thing that is immediately evident as compared to my skimmed tank is the huge variety of tiny copepods and other micro life that this tank currently supports.
At the moment I'm also trying to locate and remove a mantis shrimp that is quite happy chopping up all my fire and bristle worms, as well as some small shrimp that came in with the rock.
So far I've had a few casualties most likely due to my impatience and impulsive nature when you leave me in the local fish store, or more accurately, I simply shouldn't have put these guys into a tank with curing rock. With my current unlimited access to good saltwater I thought i could manage, evidently not, since I'm not doing changes while I sleep and I lost both the damsel and nudibranch during the first and second night.