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 We often associate algae with a slimy feeling that makes our
ponds and lakes less attractive; it gets stuck on our fishing
poles, and it makes swimming less enjoyable. Although algae
often get a negative rep, it does produce more than 50% of
oxygen in our atmosphere. However, like most things, algae are
beneficial under the right circumstances. Excessive algae growth
can cause taste and odor problems with drinking water and can
even kill fish by limiting oxygen and food.
Algae problems occur when an overabundance of nutrients
(nitrogen and phosphorus) enter the pond. These nutrients are
often from runoff of fertilized lawns, fields, pastures,
feedlots, septic tanks, and leach fields. Older ponds tend to
have a buildup of nutrients which can make it more susceptible
to algae issues.
To prevent algae problems from happening, it is best to plan to
control the issue before it becomes a problem. Methods to
prevent algae problems include reducing the amount of nutrients
entering your pond by avoiding fertilizer applications around
the pond. If you are surrounded by fields or pasture, it is
suggested to establish a buffer strip (at least 100 ft) of grass
and trees around the edge of the pond. Another option includes
water diversion terraces to direct runoff from surrounding
fields away from the pond.
If algae growth has already become a problem in a pond, there
are still options for control. One method is using fish to eat
the algae. Two fish that are used for this are Mozambique
Tilapia and Triploid Grass Carp. The tilapia must be restocked
every year as they don’t survive at temperatures below 55F, and
the grass carp will eat other food in the pond before eating the
algae, so these may not be reliable sources of getting rid of
the problem.
Another method is chemical control. This requires a bit more
work due to improper application resulting in dead fish. Two
options for chemicals are copper sulfate and chelated copper;
both should be applied in an aqueous form. The pelletized form
of copper sulfate is less expensive, but it would first need to
be dissolved in water before applying; otherwise it will sink to
the bottom of the pond/lake.
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A water test should be taken before the chemical
application is made; in hard water or alkaline water, the treatments
are ineffective as the product binds with calcium in the water. The
copper sulfate is not effective in cold water while the chelated
copper is more effective at low water temperatures.
The chelated copper stays in solution and releases
copper over a period which would help control the algae longer.
Copper is a contact algaecide meaning that the algaecide will only
kill what it comes in contact with, so when making a spray
application in is necessary to get good spray coverage. As always,
it is necessary to follow the recommended rate of the chemical
label.
Physical control is another option; however, very laborious. There
are rakes and screens to remove the algae. It is also an option to
dye the pond/lake to prevent the algae from photosynthesizing and
growing. Aeration is another option that increases oxygen levels at
the bottom of the pond/lake which increases aerobic bacteria that
feed on organic matter and reduce the amount of nutrients in the
pond.
Before applying treatment to ponds, it is a good idea to think about
how water from the pond will be used. Chemical treatments require a
waiting period for swimming, irrigation, watering livestock, etc.
For additional information or assistance with pond algae problems,
contact your local Extension educator.
[WRITER: Katie Parker, Local Foods
and Small Farms Educator, University of Illinois Extension] |
