to Control Pond Algae
This article discusses the many factors involved in controlling
algae growth in ponds. It is designed to better enable the pond
keeper to have a full range of knowledge about combating algae
Algae is one of the most talked about topics among new pond
owners. Controlling algae is usually more of a problem for new
ponds. A new pond does not have the proper balance of plants,
animal life, and general biological function.
One of the most important things that you can do when setting up a new
pond is to get the proper equipment installed. The pump
you install should move at least 1/2 of the total pond volume for a water
garden. The term “water garden” is assumed to be a pond with lots of plants
and some fish. A koi pond usually has few plants and large fish requiring
more filtration than a water garden. This type of pond is better off moving
at least the full volume of the pond each hour. [Pond
Besides moving the water you also want to filter the water. The pump
should move water through a filter that is sized for your pond. See How
to Select a Filter for a page that provides choices for several
pond sizes and filter combinations for you. Biological filtration takes
several weeks or months to mature to the point that it makes a major improvement
on your water quality. The filter needs to run 24 hours a day 7 days a
week to work.
Another major consideration for creating
good water quality in the pond is one that is properly constructed.
A pond should have about 40% of its surface area for the deep
zone, which should be at least two feet for a water garden and
three feet or more for a koi pond. Thirty percent should be an
intermediate depth of 1-1/2 to 2 feet and the remaining 30% at
least 1 to 1-1/2 feet deep. A slight slope to the deepest level
allows for easier removal of debris from the pond [
skimmer is highly recommended as it can remove up to 85% of debris before
it sinks. The pond should be constructed so that rainwater does not flow
over the yard and into the pond. This is one of the more common causes of
algae in the pond. Rain runoff carries with it lots of organic debris that
contain nutrients that feed the algae. Also fertilizer or chemicals could
be carried into the pond causing problems. If your pond is already constructed
you cannot do much about the depths of the pond but you can alter the area
around the pond to make sure that runoff does not flow into it.
A pond built using concrete, limestone, or marble will also tend to have
a high pH,
which can contribute to greater algae growth.
debris buildup in the pond bottom is normal. As long as this sludge is
no more than 1/4 inch or so physical removal is not necessary. In a properly
constructed pond this debris ends up in a fairly small area where it can
be removed when necessary. Course material like string algae and dead
leaves can be removed with a net. A skimmer
net or algae net does a good job of this. If the debris is
too fine to be removed with a net then a pond
vacuum works well. Using the following products should reduce the
sludge and keep it to a minimum. The regular use of bacteria and enzyme
products like EcoFix,
PondZyme , Microbe
Lift line of products
Clear is not only good for the overall pond water quality they
also help reduce odors, improve the health of the fish, reduces the amount
of sludge in the pond which would otherwise promote algae growth. Learn more by reading our article on pond sludge
Proper Plant Balance
If you have a water garden and not a koi pond then make sure you have
the right types and numbers of plants in the pond.
Anacharis or other underwater plants and floating
plants remove excess nutrients from the pond by absorbing these
nutrients for their own growth and starving the algae for its food source.
Also provide approximately 2/3 surface coverage using water
lilies, floaters (like Water
Lettuce or Water Hyacinth),
or other plants that shade the surface of the water. These plants reduce
the amount of sunlight that penetrates the pond; this helps keep the water
cooler and starves the algae for sunlight.
[Pond Surface Area
Even though you have set up your pond using the right components,
have added the proper type and number of plants, and do not have
an excessive number of fish you could still have some algae. This
is especially true when a pond is young. Other methods of algae
control may be called for during the first few years of a pond.
As a pond matures (as long as it hasn't been totally emptied and
refilled) the algae gets less and less and may no longer be a
Additional Algae Control Methods
What can we do while we are waiting for our ponds to mature? One thing
that every pond owner should do is to add beneficial bacteria and enzyme
products, as mentioned in the maintenance section above, to their pond
on a regular basis. Not only is this good for the overall pond quality
it reduces odors, improves the health of the fish, reduces the amount
of sludge in the pond, and reduces the algae. If your problem is green
water then you can solve this easily by installing an ultraviolet
sterilizer. This is the only way to guarantee clear water
100% of the time [More
information about UV sterilizers].
Filamentous algae have many algae cells attached together. It
comes in many forms, it can be long and stringy, it can be short
and furry or in the shape of webs or mats. The short velvet type
of algae that covers the liner and everything else in the pond
is beneficial. It helps provide a natural appearance to the pond.
It uses nutrients from the water, provides oxygen during the day,
and the fish nibble on it. This type of algae cannot be totally
eliminated with fish and plants in the pond. String algae, which
may coat the waterfall, is a little harder to control. You can
physically remove it from the pond where possible. Filamentous
type algae will flourish on waterfalls and in shallow streams
because the sunlight is more intense providing more heat and light
than what may be in other parts of the pond and there is a constant
supply of nutrients flowing through it. GreenClean can be very effective in treating filamentous algae on the waterfall and stream.
We carry other
products that will control algae during the time that your
pond is maturing. Algaway is probably the most effective. Barley
Straw and Barley
Straw Extract can also be effective in improving water conditions
for most ponds. Pond Dye shades the water, which limits the amount of
sunlight feeding the algae. We carry blue
dye, this is a cost-effective solution in large ponds and lakes,
but it can be used in any pond. When treating for algae it is very important to ensure you have adequate aeration and do not exceed package directions.
If your pond does not contain fish then
is a great product to use. This product is safe for pets that may drink
from the pond but not for fish.
Remember that fish
and fish food add nutrients to the pond, which in turn feed algae. Don’t
add more fish than your pond and filter will support and don’t overfeed
Yet another means of algae control is a pond Ionizer. Ionizers can reduce algae growth by releasing a measured amount of minerals to the water.
- Keep the organic load down by keeping runoff out of the pond and
the sludge to a minimum. vacuum
sludge that has already accumulated. Less than 1/4 of an inch of sludge
on the bottom should not be a problem.
- Don't over feed or keep more fish than your pond will support.
- Install a large biological
filter and give it time to work, this could take several
- Use enough, and the right type of, aquatic
plants. This means surface plants for shade and floaters
and underwater plants to remove excess nutrients.
- Use biological
treatments and give them time to work. Microbe-Lift
will help but this is an ongoing process and takes time along with the
methods outlined above for balancing your pond.
- Use AlgaeWay
to eliminate existing problems more quickly. Barley
Straw Extract can be used in ponds less than 3000 gallons.
- Install an ultraviolet
sterilizer for the most effective control of singe-cell
(green water) algae. [More
information about UV sterilizers.]
Pond Shelf Depth Illustration
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