On Sun, 13 Aug 2006 18:13:24 +0800, "DK" wrote:

One problem that I face now is the emergence of numerous free-floating
clumps of green algae every afternoon (after strong sunlight) which I would
scoop out manually using a net on a long pole. It is very irritating but
strangely, if left alone these clumps of algae seem to disappear by
nightfall. Beats me. What are these actually ? Are they called algae scum
(read it somewhere) and how do they come about ? Are there anyone out there
who have experienced the same predicament & how did you deal with it ? The
filter of the UV filter gets clogged up very quickly too. Wonder if the
reason could be the size of the pump or something else.

I've converted a hot tub to a lily pond with a few small goldfish for
mosquito control and have the same problem. Almost every year I have
an algae bloom (the microscopic kind that in the billions turns the
water green.) in my 1500 gallon pond and my solution is to use
aluminum sulfate to kill the algae and remove the dead stuff with a
shop vac and pond filter. The aluminum sulfate doesn't always get rid
of the string algae (the floating scum.) Most people here advise to
take it out manually and that is probably a good idea in most
instances, since killing all the algae that forms on the sides and
bottom removes a plant that consumes ammonia without it having to be
converted to nitrates.

My lily pond OTOH is for viewing plant life and not fish, in this case
the fish are there for mosquito and other insect control and could be
replaced with dunks. I'm convinced the algae causes negative growth
results on water hyacinths and other plants too, so I'm using
AlgaeFix, since the label says it will kill some forms of string
algae. Not sure this is the best solution, but after a week the water
hyacinths are putting on green color on the leaves coming out of the
center.

I hope you the best of luck with your pond and would like to suggest
an article about green water by a member of the San Diego Koi Club.
http://www.koiclubsandiego.org/library/green_water.php

Regards.

Hal