I bought a house with a man made pond about 15' in diameter. 60% of
the surface covered with either pond plants or shade from surrounding
trees. I have a waterfall pump circulating water from one side through
a hose to the other side where it spills it back into the pond.
Unfortuneatly, the surface has been growing a green algae and also
thousands of tiny yellow/green seeds or leaves are in the pond. Are
those tiny seeds part of the algae or a product of one of the pond
foliage? I currently don't have any fish in the pond; would adding
fish make that go away? If not, what can I do to keep it relatively
clean?
thanks!!

Can you take a picture and post it to a website? I'm wondering if you have
duckweed rather than algae. Google for a picture of that or Azolla. ~ jan

I'd think you're right on this.

This is my favorite duckweed page, quite comprehensive:

http://www.mobot.org/jwcross/duckweed/duckweed.htm

As for the getting rid of it, Koi might eat it. Or they might not.

Duckweed appreciates still water, so upping the tempo on the waterfall
might help.

Finally, whatever it is -- Duckweed or not! -- requires nutrients to
grow. That it's growing so heavily implies nutrient-laden water

Get a bigger filter. You don't have to buy one, read he

http://www.pondsolutions.com/bog_filter.htm

And he

http://www.google.com/search?hl=en&q...=Google+Search

As a last resort (only look to this /after/ proper biofiltration
is in place for your pond), read he

http://www.emperoraquatics.com/whati...rilization.php

C//