Ponds and lakes need vegetation
Lake weeds
Some vegetation in a pond or lake is a good thing. Not all vegetation is bad. In fact, you need about 20% of the pond area to be vegetated for the pond to carry on the natural life cycle needed for a healthy aquatic environment. These "lake weeds" provide oxygen, food, and cover for fish and other aquatic life, and are only a problem when they get out of control.
Algae
Lake weeds are not the only vegetation in a pond or lake. There is another type of vegetation necessary to have a healthy aquatic environment. Algae. There are many different types of algae. Some, like phytoplankton, are single cells that remain suspend through much of the water profile.
Phytoplankton
Phytoplankton provides food
These provide food for micro invertebrates, which are consumed by bugs, which are then consumed by small fish, which are then eaten by larger fish, and, if you eat fish, they are consumed by you.
Phytoplankton provides oxygen
Algae also provides oxygen where it is needed most, right there in the water where the fish and other forms of life live.
Phytoplankton provides color
One of the most important services provided by phytoplankton is the green tint it adds to the water in a lake. This green color provides shading for the creatures in the water, and prevents sunlight from penetrating to the lake bed. This function prevents excessive weed growth, and helps prevent other algae problems like pond scum.
Filamentous algae
Filamentous algae goes by several common names. It is most often called pond scum, or blanket weed, and is sometimes called string algae, or lake slime. There are many other regional variations. It is single cell algae that tends to join together with other cells producing a mat that rises to the top of the pond because of the air produced underneath it. This type of algae is normally considered to be bad, especially if it covers large portions of a body of water.
Upright algae
There are a few types of algae which grow upright similar to a vascular plant. Among them are Nitella, otherwise known as Stonewort, and Muskgrass, also known as Chara, or Skunkweed. These are often confused with other types of lake weeds, but normally pose very few problems for the pond manager.
Some vegetation is good, but too much can cause serious problems for you and your fish and your recreational activities. See also: Vegetation Control.
