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All About String Algae

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General Characteristics

Spirogyra are comprised of cylindrical cells that are connected end to end, forming a long, thin, green filaments. This algae is commonly found in fresh, clean water and tends to grow in large, slimy masses. In the spring, the spirogyra begin life underwater, though as the water warms, the plant produces large amounts of oxygen, which becomes trapped in the filametous masses. The trapped oxygen gives the tangled mass buoyancy and thus the tangled filaments rise to the surface in one large mass. Different species can grow and become entangled in the same mass.

Where it Comes From

Spirogyra reproduce both sexually and asexually, releasing spores into the environment. String algae spores are extremely durable and can remain dormant in the environment for many years becoming active after being introduced into water. This is why backyard ponds can be blanket weed free for years before becoming infested. Unfortunately, removing the algae actually releases more spores into the environment, increasing the chances that your pond will become infested again within a matter of days.

Removing Spirogyra

Spirogrya proliferate quickly under the right conditions, quickly becoming unmanageable. The main problem with a string algae infestation is that, if left unchecked, it can quickly deplete the pond of vital oxygen, strangling ornamental plants and fish. Fish can also become entangled in the algae, causing death. Plus, it just looks bad.  For these reasons, blanket weed must be removed from your pond.

  • Manual removal: The easiest method for removing string algae is by pulling it out. However, this method is extremely ineffective for long term control. Manual removal of spirogyra releases spores into the environment, which will cause another infestation within a couple of days.  This method is good for removing the big chunks before you apply beneficial bacteria.
  • Algaecides: There are a number of chemical solutions available to help control string algae as well; however care must be taken to prevent harm to other plants and aquatic life.
  • Limit growth naturally: One of the most effective ways to treat string algae is to create unfavorable growing conditions. Creating artificial shade sources to limit your pond’s exposure to direct sunlight as well as adding oxygen to the water will help stunt growth. Also, you can introduce other plants into your ecosystem that will compete with the algae for food and other resources. Reducing the number of fish in your pond will also help since string algae thrive on fish wastes and uneaten fish food. Installing a large biological filter and seeding it with beneficial bacteria will also improve the water quality in your pond and reduce the chances of a blanket weed infestation.  We recommend Aquascape’s SAB (String Algae Buster).
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