Articles, Blog

Controlling Algae in Farm Ponds

August 28, 2019


Hello, my name is Todd Sink and I’m the Fisheries
Extension Specialist with the Texas A&M AgriLife Extension Service. As you can see here it’s
spring time in Texas most of the trees are beginning to bud out and most pond owners
are once again getting back out to visit their ponds, and many of you are seeing an all
too uncommon problem. Some people call it moss, some people call it pond scum, but what
it is in fact is filamentous algae. Today with my crack team of undergraduate students,
we will be showing you how to identify the various types of algae and how to manage it
in your pond setting. Hi, my name is Jesse Gwinn. There are three different types of
algae commonly found in farm ponds and small lakes. These are filamentous, planktonic,
and macro algae. Filamentous algae are made of single cells that form long visible chains,
threads, and filaments that intertwine to resemble wet cotton or wool. This type of
algae grows along the bottom of the pond in shallow areas, and then floats to the surface
to form mats commonly referred to as pond scum, or pond moss. This type of algae is
unsightly and may interfere with swimming, fishing, or other recreational activities.
Hi, my name is Mikayla. Another type of algae you can encounter in your pond is plank-tonic
algae. This algae is microscopic and free floating algae that exists in the top few
feet of a pond or lake where the sunlight penetrates. This type of algae is normal and
in fact desirable and essential for the ponds food turret as it provides food for microscopic
animals that are eaten by fish fry and other pond inhabitants which ultimately support
a larger fish population. They exhibit seasonal abundance, often blooming in the spring and
sometimes summer, coloring the pond different shades of green, blue-green, or brown. The
natural degradation of the algae blooms can lead to oxygen depletion and fish kills in
the pond. Hi, my name is Hannah. One of the types of algae that you can encounter in your
pond is macro-algae. There are two main types of macro-algae found in Texas ponds. Chara
and Nitella. Chara, or Muskgrass is a grey-green branch, multicellular, macro-algae with whirled
branches that is often mistaken for an aquatic plant, but can be distinguished by it’s lack
of flowers. It has a grainy, or crunchy texture, does not extend above the water surface, and
has a musty, almost garlic-like odor. Chara prefers alkaline, hard-water ponds and grows
in rows along the muddy bottoms in calm waters. It is an undesirable species because it carpets
the bottom, crowds out other species, and grows rapidly, quickly becoming a problem.
Nitella is another type of multicellular, macro algae that are branched, do not produce
a flower, and do not extend above the waters surface. Also known as Stoneworts, this algae
has no odor, is soft to the touch, and light to dark green in color with forked, bushy
branches. Like Chara, it grows in rows, attached to the muddy bottoms of calm waters, and is
undesirable because it can carpet the bottom of the pond and crowd out other desirable
species. Biological controls for macro algae and filamentous algae include Mozambique Tilapia
and Triploid Grass Carp. Mozambique Tilapia will consume some filamentous algae and some
macro algae, such as Nitella, but typically provide limited, if any control. Additionally,
as a warm water speices, Mozambique Tilapia cannot survive in temperatures less than 55
degrees farenheit. So in all but far southern Texas climates, they must be restocked each
spring. Triploid Grass Carp will eat filamentous algae, but because it is not a preferred food
item, they will consume other types of submerged vegetation before filamentous algae. Therefore,
they are not typically a reliable control for filamentous algae. However, Grass Carp
readily consume macro algae such as Chara, and Nitella. In Texas, only Triploid Grass
Carp are legal and a permit from the Texas Parks and Wildlife Department is required
before they can be purchased from a certified dealer. Mozambique Tilapia are the only legal
Tilapia species that may be purchased in Texas for pond stocking. Another way of controlling
your algae is through chemical controls such as copper sulfate. When using copper sulfate,
the aqueous form is recommended. Although it may be cheaper, the granular form requires
more effort because it must be dissolved in water and then sprayed onto the pond. Copper
sulfate only works as long as it is in the water column, so if crystals or pellets are
thrown into a pond, they will will sink to the bottom where they will not be effective
in controlling algae. Copper sulfate is not effective in hard or high alkalinity waters,
because it binds with the calcium in the water, forms a precipitate, and renders the copper
ineffective as an algaecide. Copper sulfate is not effective in cold water. It’s toxicity
to fish also increases with higher water temperatures, and it should not be applied during the summer.
Another method of controlling algae is chelated copper. Chelated copper comes in an aqueous
form that must be sprayed over the pond. Unlike copper sulfate, Chelated copper doesn’t precipitate
in high alkalinity waters. It is also more effective in waters with lower temperatures.
Chelated copper stays in solution and remains active for longer because it releases the
copper ion more gradually than copper sulfate. When applying your copper compounds to pond
algae, you can either use a hand pump style sprayer or a backpack style sprayer such as
this, or you can use a larger, commercial type sprayer that either goes in the bed of
a pickup truck, or on the back of a 4-wheeler. When you’re applying copper, it is important
to remember that copper is a contact herbicide, so it’s only going to be active on the algae
that it actually comes in contact with. Therefore it’s important not just to dump it in the
pond, you need to spread it over the surface of the algae which means you need to spray
it on. Remember, when you’re using copper sulfate, I want to stress again, you need
to dissolve crystals in water before you apply it and then spray it on. As you can see in
this instance here, we already have a chelated copper complex mixed up with our water, copper
algaecides do have a blue color due to the copper in them, and it is very important not
have these compounds come in contact with your skin because it will dye you blue and
you will look like a smurf for a long period of time. Always make sure you use proper safety
attire and make sure you wear a good set of gloves. All copper compounds can be toxic
to fish if they are used above the labeled rates. Be sure to test the ponds alkalinity
and adjust copper treatments to alkalinity concentrations. Be very cautious when treating
a pond with an alkalinity of less than 50 ppm, as copper can be toxic to fish. Never
treat ponds with an alkalinity less than 20 ppm. Above all, follow all label instructions
when applying chemical controls. Aquatic herbicides are not toxic to fish when properly applied
according to the label. A final way to control the algae in your pond is through physical
control. Filamentous algae and macro algae can be physically controlled by using a rake,
a seine, a wire screen or another similar device, or by physically cutting the algae
or removing it from the pond. However, physical control methods such as these are generally
laborious and short lived, as the algae will recolonize very quickly afterwards. Many companies
make cutters and rakes that can be used to remove the algae from the ponds. Another method
of physical control involves using non toxic dyes and colorants to shade the pond and limit
sunlight penetration that promotes the algae growth. Dyes and shading products are made
by a company such Aqua Shade, Blue Springs, or Crystal Blue, however this sort of control
method may suppress the natural food chain of the pond by reducing the plank-tonic algae
that food chains of the ponds are based on. Shading the pond can also be achieved by using
a physical barriers to sunlight penetration such a shade mat. Prevention is usually easier
and more effective than treatment. The most important key to preventing the growth of
algae is to reduce the amount of nutrients entering the pond. Creating a 10 to 20 foot
buffer around the pond with taller vegetation to filter excess nutrients, reducing the amount
of fertilizer used in drainage areas of the pond, and locating septic fields far away
from ponds can help keep the excess nutrients from entering the ponds. Another option is
to aerate the pond. Aerating with a bottom diffuser increases the level of dissolved
oxygen at the bottom of the pond, which in turn increases the number of aerobic bacteria.
These bacteria feed on organic matter such as decomposing plants and reduce the amount
of excess nutrients released into the water. Algal growth may also be prevented by steepening
the sides of the pond during construction. A slope with a 3 to 1 decline helps to eliminate
shallow areas that can be penetrated by sunlight, and can discourage the growth of algae.

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