~ jan JJsPond.us wrote:

Matt, There IS a whole lot more to it than just tossing in more plants. One
possibility: if your pH is too high or too low most plants can't take up
the nutrients. As a pond matures "usually" the pH comes down due to the
breaking down of organics, and thus the plants start taking up more
nutrients, the algae can't compete and clear water results. The filter
coming on line could have just be coincidental, but I'm sure it helped
regardless. Bio-filters have more areas for bacterias that break down
ammonia to nitrite and nitrite to nitrate to live on. Without getting to
technical, nitrate is what plants easily feed on.

Do you have a pH test kit?

Yes, the ph is fine. So is the hardness. There is no, and never was,
any measurable ammonia or nitirites or salt or a problem with chlorine
or dissolved oxygen. I don't have any other tests.

Have you read these pages?
http://www.koiclubsandiego.org/H2oQual.html

Yes I have. Furthermore, Norm Meck, who wrote that web page, also wrote
another (http://www.koiclubsandiego.org/GRENH2O.html) with a
description of how algae is killed from a byproduct of rotting algae and
a type of bacteria (not the ones that remove ammonia) found in filters.
He disagrees with your comment that "the plants start taking up more
nutrients, the algae can't compete and clear water results". It's more
along the lines of dead algae gets caught in the filter, heterotroph
bacteria feeds on the dead matter, and some substance is released into
the water that kills algae. So, full sun is fine and lots of nutrients
in the water is also fine.

Experience with my pond follows his theory to a T and doesn't agree with
the usual descriptions of pond chemistry I find on the net.

So, given that Meck's description of how to get rid of algae disagrees
with conventional wisdom and it more closely describes what happened in
my pond, I think it's fair to say there's more going on than most people
realize. Conventional wisdom says put in plants to remove algae and I
suspect it's more along the lines of remove the algae so the plants have
a chance to grow. If people put the plants in via a veggie filter then
they've also added the mechanism to kill the algae. If instead they add
the plants without a place for the algae to rot they will continue to
have green water (my experience). When someone asks how to get rid of
green water and the response is add water cress and hyacinth I suspect
it won't work (also my experience).

Matt