Algae

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Hundreds of different kinds of algae occur in all fresh waters in Mississippi. These plants cause most of the problems in private and commercial fish ponds. Excessive algae growth is generally called "pond scum" or "pond moss."

Because of the number of different kinds and the difficulty in controlling several kinds, it is best to identify them accurately before treating. However, the treatments listed will control most kinds of algae you will find.

Following are the main types of algae:

• Plankton algae - these are minute, free-floating plants that give a green, bluish-green, or brown color to the water. Use chemical control a, b, or c listed on the treatments page.
• Filamentous algae - these are long strands, filaments, or nets of plant material that may form floating nets. Use chemical control a, b, c, or d.
• Muskgrass - a branched alga that resembles flowering plants. It has a stem with whorls of leaves or branches. The two most common kinds are Chara, which feels rough and gritty, and Nitella, which is smooth. Click here to view photos of muskgrass. Use chemical control a, b, or c.

A common cause of excessive amounts of filamentous algae in farm ponds is use of a fertilizer with high nitrogen content, especially in waters with low alkalinity. Switching to a fertilizer such as 0-46-0 (triple super phosphate) may help alleviate the problem.

Some species of algae are difficult to control. These are usually coarse and tough such as Pithophora and Cladophora. Best control of persistent algae is obtained with treatments (c) or (d). Treatment of troublesome algae will also typically impact beneficial microscopic algae called "plankton." Death of plankton algae can result in rapid oxygen losses in ponds, which can lead to fish kills. Take care when treating not to kill too much algae at one time, creating increased biological oxygen demand (BOD) that can deplete oxygen. A good rule of thumb is to treat only one-fourth to one-third of the algae, then wait 7 to 10 days before treating again.

Specific kinds of algae can be effectively controlled using grass carp as an alternative to chemical treatments. Grass carp are highly effective in controlling muskgrass (Chara spp.) and stonewort (Nitella spp.), but are ineffective at controlling planktonic and other forms of filamentous algae. Generally, 5 to 10 grass carp per surface acre will control weeds. See publication 1894 - Grass Carp in Mississippi Farm Ponds for more information.

Professionals have given particular attention to make certain all herbicide treatments have been registered with the Environmental Protection Agency for use in the manner described. Registrations for specific practices are often changed or deleted; therefore, treatments suggested in this information sheet may not remain current indefinite. Read and observe the manufacturer's label to prevent misuse of a herbicide. It is not intended or proposed that usage of any given practice suggested in this information sheet be in violation with existing registration or manufacturer's label.

If you fail to carefully read and follow suggested treatments, you could cause extensive damage to the environment, crops, livestock or humans.