I have been trying to make a good filter for my fish pond for a couple of years. The fish water was like green soup and you could not see the bottom. Sand filters cleared the green somewhat but they blocked up over a couple of days and it was a chore to clean them. . What to do? First I tried azolla but I did not try it long enough. Next I tried a "swirl pool" to settle out the bigger stuff. It did not work well. At some stage I introduced a few waterfleas to the swirl pool.
Step 1: This Is the Side of the Swirl Filter 3 Weeks Later.
No green in the water and you can actually see the bottom. Unheard of before!
Step 2: How Did It Work? Edible Filter!
I airlift water up to the swirl tank, it spins around in it and the water fleas eat the green stuff. There are thousands of them! If they get into the overflow, they end up in the pond and then shortly afterwards, they end up in a fishes belly! Edible filtration! See the video for more details