I wouldn't put anymore than 2 or 3 fish in there. Maybe a couple of clowns and a goby or something. I would say about 15 or 20 pounds or rock. If you have a JBJ nano cube, what I did was put 15 pounds of liverock in the main part of the tank and about another 7 or 8 pounds of rubble rock in the filter compartment. Rubble rock is the smaller pieces of live rock that breaks off during shipment. Ask your LFS if they sell it, mine does.