Mosquito Fern or Azolla is a small free-floating plant approximately 1 to 3/8 inches wide. Leaves overlap giving a quilted look to the surface and hide the stem. A single root protrudes from each stem. Mosquito ferns can vary in color from green to red and are generally found in quiet ponds protected from wind action.
They can be aggressive invaders and are often found mixed in with duckweeds or watermeal. If these fern colonies cover the surface of the water, then oxygen depletions and fish kills can occur. Mosquito fern has no known direct food value to wildlife.
Chemical control is recommended.