The lack of FA was due to the very turbid (muddy) water conditions created by the bottom rooting fish. The RESULT was a reduction in FA. The REASON was a lack of light penetration allowing FA growth and not an "algae eater".
Rainman my pond was turbid somewhat but I believe the visibility was probably 2 feet, but I didn't measure it doing the 15 years of being FA free. I, the kids & grandkids were feeding the fish from the deck and we could see the fish, but they were big fish and easy to see. There were minnows and bluegill also being fed and seen. I fed the fish every day except when they stopped feeding when the cold water arrived. If you want to believe the FA was only accidentally eaten that's fine but the bottom line is there was only trace FA for all those years. The pond was total free hands off maintenance. I never sprayed, I never pulled or cut anything and it always looked nice. My pond friends also didn’t believe. We had a beer fest on the deck so they could observe and ask questions. Only now is the pond out of control. Cattails, spatterdock. But I may like a lot of cattails.
Here is a short video showing my Corkscrew ell grass. It has spread and grown better then I expected. The water clarity is 3 foot because of the tannin. Earlier in the year it had been clear to 6'4".
http://www.youtube.com/watch?v=4BTIKiXk2Yc
