10 Reasons to Control Pond Weeds & Algae


Pond weeds and algae affect property value. If your pond on the rural property or the retention pond in your neighborhood has an overgrowth of weeds and algae, it will negatively affect your property value. It has a sloppy appearance, and is perceived to be “swampy, snakey, or stagnant”. Whether or not a potential homebuyer can articulate why they are disturbed by the unkempt look of a pond or lake, they perceive it and will request that it be remedied, or simply walk away. Buyers with some pond knowledge will recognize it as deferred maintenance and request a fix or a discount. Not selling your house? If your neighbor discounts the sales price of his, your property value is still affected because it is an adjacent, comparable property used to determine the value of your home.

Some algae produce toxins. Blue-green algae specifically has certain species that can produce toxins affecting the brain, skin, and liver. They can affect humans, pets and wildlife. In certain public lakes, swimming is eliminated after monitoring detects blue-green algae at certain levels. Water-loving pets like labrador retrievers can be exposed and then lick the algae off their fur, becoming quite ill. Blue-green algae also affects wildlife poisoning, feeding ducks, and even the bald eagles that feed on these ducks.

Interfering with fishing-hooking and access. This has to be the top aggravation for fishing and has caused a lot of cussing in ponds everywhere. Who hasn’t fished through the frustration of pulling in “pond moss”/filamentous algae after every cast? Pond vegetation that grows too heavily around the edge can snag your best bait. Pond weeds in a heavy infestation can cause you to lose your record fish after you set the hook, tangling in a heavy mass that is impossible to land. After a struggle, the line either snaps or you give the fish too much time to thrash and get off the hook. If weeds are everywhere around the bank, shoreline fishing is pretty much eliminated.

Pond weeds are filling in you pond. Most plants, even in the southern United States, will be reduced with cold winter temperatures. This material dies and sinks to the bottom of the pond as a “liquid compost”. This degrades into pond-filling, pond-polluting sludge. These same plants have seeded in and will return in the spring to grow more aggressively each season. Every year these plants lay down another layer of nutrient rich fill to promote weed and algae growth in your pond. Problematic areas like shallow shorelines and narrow inlets will revert to land after several seasons.

Pond vegetation can cause oxygen depletion. So, while green plants do make oxygen during sunlight hours, they respire at night, consuming oxygen. Submersed plants, including most algae, generate oxygen in the water column when exposed to sunlight and respire at night as well. During cloudy days though, this can be a net loss of oxygen. Also, seasonal die-off of vegetation makes a mass of decaying vegetation in the pond, which if allowed to build up, can act as a sponge for oxygen in the pond. During seasonal mixing of the pond, or when ponds are mixed by storms, the chemical and biological oxygen demand from this material can be distributed in the pond water column and completely remove oxygen. Fish need oxygen to thrive and to survive. Low oxygen conditions will stress and stunt fish populations at the very least, and a complete loss of fish populations is possible with an oxygen-related fish kill. Blue-green algae are a poor producer of oxygen and shade out more beneficial algae in the pond, making them a particularly threatening issue.

Algae can make your fish taste bad. Blue-green algae specifically produce compounds that are accumulated in fish, and give them a musty or muddy flavor. Older fish will have more time to bioaccumulate these compounds. It is not pleasant and can be a real turn off on a fish fry. Fish that are no longer exposed will cleanse themselves off the off-flavors, and their taste will improve.

Pond vegetation can interfere with fish populations. Too much vegetation can interfere with our ability to remove fish from the pond, but it can also interfere with predator fish being able to harvest prey fish if they have thick cover. This can result in an overpopulation of bream/bluegill and skinny largemouth bass that use them for food in a healthy habitat.

Pond weeds and algae clog pumps and aeration. If you have an irrigation pump or pump for a water feature, there will be an intake screen to protect the pump from debris. This can become easily overwhelmed when contacted by a mat of algae or a large clump of pond weeds. Floating fountains are a common feature in ponds and lakes, and while they are generally designed to handle a greater amount of debris, they too can become blocked and require cleaning. Smaller amounts of algae can enter irrigation lines and clog irrigation heads throughout your landscape.

Aquatic vegetation will continue to grow. Plants grow. Aquatic plants and algae grow fast. If you have an undesirable plant in your pond it can spread rapidly and cause a serious transformation. Duckweed, Salvinia, Water Hyacinth, Watermeal, Water lettuce, Azolla, and nuisance algae can cover a pond in rapid fashion (30-60 days). Monitoring and addressing this early can avoid a large liability.

Pond weeds provide habitat for snakes and mosquitoes. Shallow areas producing large amounts of vegetation will provide protective cover and food for aquatic snakes. While most are non-poisonous, they are generally undesirable. Mosquitoes in open water in your pond are not a problem. Adults landing on the water or larvae swimming in the water would quickly be consumed by fish. However, in shallow areas dominated by aquatic weeds and algae, mosquitoes can lay eggs and successfully hatch larvas since fish are unable to access them. The decaying organic matter produced by heavy vegetation produces gas byproducts that actually attract mosquitoes to the habitat as a favorable place to lay eggs. West Nile virus is increasingly in the news and is a real health risk. Avoiding the culture of mosquitoes is wise.

The entire surface of this pond is green due to the full coverage of duckweed.


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