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How You Can Control Pithophora

Updated on March 15, 2015
Horsehair algae
Horsehair algae | Source

Once you have a pond, you have to be aware of the species of algae you might encounter. Stubborn pond algae are the worst you can have in your backyard water feature. These are also known as resistant algae. One of these pond nightmares is Pithophora, commonly called horsehair algae, stag horn algae , thread algae, or cotton call algae. It is classified under Cladophoraceae. Pithophora have irregular branched out threads from a single attachment. Long, thick strands grow and resemble hair, with the texture of wool. If your pond water is rich in iron, expect Pithophora to thrive.

Horsehair algae are green filamentous algae, which are found as dense mats, floating on the surface or growing on the pond’s bottom. Under the microscope, Pithophora have filaments with akinetes (reproductive cells similar to spores). You may see them as lime green or dark green with a tinge of brown. They are found on the surface of the water because of the buoyancy brought about by the gas bubbles they produce as they grow. Whenever these floating mats are disturbed by heavy rains or strong winds, they temporarily sink to the bottom. The mats eventually reappear after several days.

Pithophora Habitat and Distribution

Cotton ball algae is known to be the most persistent and resistant species of pond algae that you can ever encounter. It can be found statewide, from piedmont east to the coastal plains. It is usually happy in low flow, shallow ponds, which are rich in phosphorus and nitrogen. You can find large Pithophora mats during the summer. This prolific algal growth usually interferes with recreation, irrigation, and fishing activities.

Stag horn algae mat
Stag horn algae mat | Source

Inorganic Control of Stag Horn Algae

Below are some of the most effective inorganic control methods for Pithophora takeovers in ponds:

  1. Diquat dibromide. This form of Pithophora control has diquat dibromide salts as active ingredients. About one to two gallons are enough for one surface acre. It is always better to treat your pond during the early stages of Pithophora infestation. If you do this, you can consume less diquat dibromide. The most difficult part to kill in horsehair algae is the bottom. The mats on the surface of the pond can be sprayed evenly with diquat dibromide. Make sure you mix in a non-ionic surfactant with it (1.5 to 2 pints for every 50 gallons of diquat dibromide. Remember that you should avoid applying this herbicide in muddy water because it will be inactivated.
  2. Copper chelates. This inorganic control method has elemental copper as its active ingredient. Take note that when you use this product in soft water, its toxicity increases. If the pond water has less than 50 ppm of alkalinity, you should not exceed 0.8 ppm of the product. Just spray the surface mats with your desired concentration. Make sure you mix it with the right amount of water for superior coverage. A treatment every week or every week is necessary, if your pond needs it.
  3. Chelated copper and dibromide. You can combine these herbicides with a ratio of 2:1—2 parts chelated copper and one part dibromide.

Cotton ball algae clumps
Cotton ball algae clumps | Source

Pithophora Causes and Their Treatment

Here are treatment methods treatment methods for each cause of Pithophora takeover in your pond:

  1. Nutrient imbalance. Whenever there is an excess or deficiency of nutrients in your pond, expect the Pithophora to emerge. If you want to correct this, you should test your pond water for phosphate and nitrate content. If these two elements are high, improve your maintenance and make a few changes in your water. Excess iron in the pond water is also a major component in Pithophora growth.
  2. Flow of water. If your pond has low flow or movement, you should increase the flow, so that you can prevent the buildup of nutrients.
  3. Light allowance. When your pond is established in a spot where there is abundant sunlight, expect a proliferation of cotton ball algae. Like higher plants, algae make their own food through photosynthesis. You can reduce the light coming in by installing shade over your pond water or by using pond dyes. Without sufficient light, Pithophora cannot produce food. They will die because of starvation.

You can also physically remove stag horn algae from your pond. Yet, you should administer treatments immediately to prevent these algae from growing back. Also consider incorporating Cherry Barbs and American Flag Fish are known to consume horsehair algae. These fish can just eliminate the Pithophora, already present in your pond. They cannot prevent the algae from growing and taking over your pond again.

Thread algae
Thread algae | Source

Mechanical Control of Pithophora

When you decide to use mechanical control of Pithophora, you should concentrate on removing the enormous buoyant clumps or mats with the use of a rake. You should do this consistently and regularly during the algae’s growing season. Pile up the horsehair algae you collect and use them as mulch for your garden.

You can also make the sides of your pond a little steeper, so that you can prevent shallow areas in your pond. If there are fewer shallow areas, sunlight is prevented from reaching the bottom of the pond. When this happens, the bottom growth of the Pithophora is deprived of sunlight. Use a 3:1 slope. For a distance of three feet from your pond’s shore, deepen it by a foot. A dredge or a dragline may be needed if your pond has filled up from decomposing vegetation or an accumulation of sediments.

Horsehair algae branches
Horsehair algae branches | Source

Biological Control of Pithophora

When you speak of biological control, you disrupt the growth of the plant by changing its environment—in this case, the aquatic environment. You can do this by altering certain elements in the pond. You can very well introduce a certain organism, which can control the vegetation in the water.

One way to change the environment is by encouraging the bloom of microscopic animals and plants, which make the water turbid. If the water has reduced clarity, there is less sunlight entering the pond’s bottom area. This significantly affects the food production of Pithophora. The blooms have to be maintained, so that the turbidity of the water lasts.

Another method is to control the flow of additional nutrients from outside the pond. Lawn fertilizer, agricultural fertilizer, septic systems, rainfall, and domesticated animals all contribute to the increase in pond water nutrients. You can install a gutter system around your pond, to prevent these nutrients from flowing into your pond water. If your septic system is close to your pond, make sure that you maintain your septic system regularly, so that backups and septic flooding can be prevented. Wastewater easily adds nutrients into your pond water.

Thread algae accumulation
Thread algae accumulation | Source

How to Remove Algae in Your Garden Pond

American Flagfish In Action

Stubborn, resistant algae like Pithophora can make your pond experience a nightmare. Even if you check your pond regularly, other factors you tend to miss contribute to the proliferation of the Pithophora. It is ideal for you to work with your local pond expert, so that you can have total control over your pond.


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