It's no where near finished, but I am pretty happy with it so far. The big round thing is an air filter of some kind and has a ring of cardboard inside. I drilled the top so the water seeps down into it, but I think it needs some kind of wicking system to induce the water to absorb into it. I am also on the lookout for something to give it a but of a lip around the top.
My goal was to make my fountain with as few newly purchased items as possible.