FYI, although many of you are likely aware of this:

Green water occurs during unicellular algal blooms (explosive growth
and multiplication of single-celled "plants"). Algae blooms are
caused by one thing: abundant (excess) nutrients in the water column.
In most U.S. waters, including backyard ponds, the nutrient most
likely to limit algal growth (and thus blooms) is phosphorus.

Where is the excess phosphorus in green ponds coming from? From
reading this group, it appears there are three main sources.

1) Tap water carries a fair amount of phosphorus, in many cases enough
to cause some level of algal blooms. I believe most people top off
their ponds with the most convenient water source: the hose and
faucet. Put tap water into a plain bucket, and set in the sun. You
might be surprised to see what grows after a few weeks.

2) Certain metabolic wastes are rich in nutrients, including
phosphorus, and fish waste is high on the list of phosphorus sources
in small ponds. Uneaten fish food also contains phosphorus (more than
fish waste, actually). Put tap water into a second plain bucket, set
in the sun, and throw in some fish food. Compare with the first
bucket after several weeks.

3) Fertilizer inserted into aquatic plant substrates are another
source of phosphorus in backyard ponds: Tabs/stakes/etc. dissolve
quickly, far too quickly to be absorbed by plants at one time, and
the leftovers are then available to support algal blooms. Put tap
water into a third bucket, set in the sun, throw in some fish food,
and throw in half a dose of fertilizer for a single plant. Compare.

Additionally, the efforts put forth in this group often seem directed
at managing algae, rather than excess nutrients. In many cases, the
techniques come across as overly complicated and somewhat backwards.
For instance, UV sterilization. Although UV has it merits, and does
kill algae, it does nothing to address the root of the problem:
nutrient loading. Turn off the light and the bloom recurs within a
fortnight. One gets the same effect from periodic treatment with
algicides, but can have harsh consequences if applied without
precision.

Several of you post valuable information regarding nutrient
management, most notably cutting back on fish feeding and the use of
plants as nutrient filters. I see some problems with plant filter
species selection, but all in all, the idea is sound. Tweaking
current practices and including some fresh ideas may serve as the
solution many seek. I suggest further discussion on techniques for
reducing nutrient loads in your ponds, thus minimizing problems with
algae. The disinterested can always kill the thread.

Gary


"Nobody you know" wrote:

The Pea Green is driving me crazy G

My pond is 3 years old, and goes through this every year. I am using "pond
blocks" but they are not working. I have a Tetra 2.5 gallon filter (pond is
about 650 gallons). I am working on convering a 50 gallon preform into a
bio-filter. Hope that will help. The pond get a medium amount of light,
some parts of the pond are in the sun all day.

Plants are starting to come up, and I have a little hornswort and anacranis
(sp) in the upper 100 gallon area.

Will try to get some pics up on my website soon.

Ideas, suggestions???

Thanks
Marc