Pump / Filter Design

We needed to have a larger filter box than what we could typically find so we designed the following.  With +30 fish in the pond and a vertical pumping height of 4 feet, it works very well.  We need to clean out the filter media about once per month.  Below are the pictures, I think the assembly is self explanatory.  The pump is plugged into a water level sensor.  As a safety feature, if the water drops 12" the pump will shut down saving the fish.