Okay, I'm weird but, bear with me here--I bought filter fiber. I take that and put it on top, with the pebbles. It slows down the flow and, you can kinda of make it look like snow. It also takes the guck that comes up through the very think filter media (which, you can't wash out, other than the sponge. The white stuff frays). So, this helps with having to change the white filter piece so often and, it also grabs the little gucky things that get through but don't make it into the filter media.
I just clob it up on top and, it is like snow--okay, dirty snow but, it sure does help in a lot of ways. The rocks, underneath also work well if you put one on top of the fountain. It slows down the flow that way, as well.