One website I found suggested that a bog filter should be 10-20% of the size of the pond. The bigger the filter the better job it does.
I am planning on a 500 sq ft bog filter followed by an 80 stream that will have a 6" deep gravel bed. I will be planting the river bed with rice or allowing nature to plant what she wants. You could also use the bog filter as a garden as many plants would thrive with a constant supply of nutrient rich water.
The goal of the bog filter is to reproduce a natural wetlands. As long as you created the wetlands so it drains toward your pond you could create a waterfall at the highest elevation of the wetlands. There are some efficent pumps out there that would work great for a 10' waterfall. I saw one that pumps 11000gph at 300 some watts.
