The Facts

• Filamentous algae in your pond will prevent more dangerous varieties of algae, such as blue-green algae or planktonic algae. Filamentous algae is relatively simply to remove with a stick or garden tool as it clumps together tightly on the water's surface.
  
  

Identification

• Filamentous algae will float on the surface of the water and also grow around rocks and water features. It is typically bright green but may be yellow or even brown. Filamentous algae may appear in long, thin strands or resemble a thick, green carpet on the surface of your pond.
  
  

Benefits

• Some forms of pond life may feed off the filamentous algae that floats on the surface of the water. The thick mat of algae also provides an ideal cover for animals such as snails and small fish.
  
  

Considerations

• To reduce the levels of filamentous algae in your pond, use EPA-registered sodium carbonate proxy hydrate products to kill the algae, or introduce grass carp into your pond. Grass carp feed on filamentous algae.
  
  

Warning

• When the algae begins to die and decompose, it releases harmful chemicals into the water, and the decomposing plant matter rapidly depletes the pond's available oxygen, which fish and plants need to survive.