Russ -- we just went to the local farm supply stores, and bought the rubber feed tubs. I'm thinking something like 18-24 inches in diameter, and maybe 8-10 inches deep? We got the soft rubber ones because they would sink. The hard plastic ones would float until the gravel was added. As for bluegills, I sure don't know. As they nest in colonies, it seems like you could put a number of the tubs in close contact with each other, and let multiple males have their own gravel. As we've discussed on the forum, I'm not sure that it's necessary, as bluegill usually find a place to spawn even if no gravel is present. It might be sort of fun to set up the "artificial colony" and watch them spawn where you place it.
