I basically have a bio-pool that splits into 2 streams with multiple mini falls (about a foot high, 3 steps) and terminates at the pond with two 3 ft wide falls that are a 3 step drop of about 4 foot.
The actual bio-pool needs revamping. It has some dwarf cattails, arrowhead, and a thalia in it. I would like to add water lettuce and perhaps water hyacinth... but it is rather shaded.
The streams were so full of parrots feather... I had to pull some. According to Sam, he placed a very small amount in each stream just last spring! Invasive... oh yeah! But... it does seem to help with the filtration and truly IS lovely. From what I have heard... it is also practically Koi proof... one of the few plants they will not eat.
As I have a 13,000 gallon pond with a bead filter (granted, a large one)... I am assuming that a good portion of my bio filtration comes from that pool and streams. Seams to do the trick... for the most part. My water tests perfect and my pond is WAY overstocked (I plan to cull VERY soon).
Just 2 weeks ago, you could see almost 3 foot down in my pond. Then I cleaned out the neglected bio-pool. It had string algae, both living and rotting... leaves, rotting pinecones, etc. I should have just vacuumed it all out... but did not want to kill the salamanders and tadpoles! LOL
Now my water is full of "fines" from stirring up the muck, and slightly brownish green from all the tannins from the leaves and algae trying to use up the "food" I am sure I released by digging into all that silt.
In any case... I support natural bio filtration 100%. Even if only as a backup and great looking addition to a pond. If I can find out how to ship it... I will send you some parrots feather if you wish! I warn ya... watch it like a hawk! LOL