Ok, here's my pond:


Notice, there is nothing in there but substrate. Here it is from the front, sort of a "behind the scenes view":


The white stripe on the left is my eggcrate. The water passes through the substrate, to the pump, which is on the left of the eggcrate, under the false bottom. As the water is drawn through the substrate, to the left, it goes through all that substrate, essentially filtering it. Make a bit more sense now? There are no open spots for water for just flow under the substrate freely. I force it all through the substrate as an extra bio filter.


Education is the most powerful weapon we can use to change the world ~ Nelson Mandela