Virginia Aquatic Weed Control - Algae - Biological Treatments

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Bacteria and Enzymes : This is a non-chemical approach which basically involves living organisms feeding off of the excess nutrients that would otherwise be available for plant growth. The goal with these products is to reduce organic sediment on the bottom, odor control, better clarity, and overall better health for the aquatic environment. Application rates are all over the board and success is sometimes difficult to measure. Each pond should be looked at on an individual basis prior to introduction of this product and it makes the application rates not all that user friendly.  Proper calculations and measurements of your lake or pond are critical in making these applications.  Blue Ridge Wildlife Management, LLC is a licensed certified aquatic pest control company in Virginia and can effectively make this application to your lake or pond.

Fish : Sterile grass carp have been used to effectively eliminate weeds within many ponds. Contrary to popular belief, they do not like to eat filamentous algae or any other types of algae. They are mentioned here because sometimes they are the cause of a species shift from rooted aquatic plants to a filamentous and planktonic algae dominated pond. The easiest way to understand this is to assume that the fish eat the plants, excrete the waste back into the pond and algae form as a result. The nitrogen and phosphorus that was in the rooted plants has not been removed and will manifest itself in algae, which are not desired by these fish. The question is, do you want rooted plants or algae in your pond? A permit from the Virginia Department of Game and Inland Fisheries is required prior to stocking grass carp in your lake or pond.


Virginia Aquatic Weed Control - Algae - Chemical Treatments

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Dyes : This is old technology but it can work. Dyes are available in blue or black, powder or liquid, and act to shade water and reduce sunlight penetration that feeds algae growth. A side benefit that has been explored with some success is tinting the water blue or black to keep predacious birds from harvesting the fish in your pond because the birds cannot see the fish as easy. Aeration works great with dyes because it helps mix up the water and evenly distributes the dye that is added to the water. This method of treatment does not work well in ponds that are pumped from for purposes like irrigation or overflow into other ponds, because the dyes are removed during this process. Proper calculations and measurements of your lake or pond are critical in making these applications.  Blue Ridge Wildlife & Pest Management, LLC is a licensed certified aquatic pest control company in Virginia and can effectively make this application to your lake or pond.

Copper : Copper is usually the first answer most people get when they bring up the subject of algae control. Copper is toxic to certain species of fish within the minnow family as well as salmonids depending on the dosage and water chemistry.  (There are alternative products that have the same effect that will not harm minnows or salmonids.) Water with high hardness and alkalinity buffers copper from being toxic, but also limits its effectiveness. The most common form of commercially available copper is granular copper sulfate. Its effectiveness and cost as a broad spectrum controller of planktonic and filamentous algae has led to its high usage. Liquid chelated copper products are used to control a broad range of algae including planktonic, filamentous, and bottom attached types of algae. Consistent usage of some copper products can lead to bioaccumulation within the sediments and this approach is on the radar of some regulatory agencies, so a varied approach is probably the most sensible path to take.  Proper calculations and measurements of your lake or pond are critical in making these applications.  Misapplications can lead to no effect or negative effects, such as a fish kill.  Blue Ridge Wildlife & Pest Management, LLC is a licensed certified aquatic pest control company in Virginia and can effectively make this application to your lake or pond.

Diquat herbicides/algaecides : are powerful herbicide/algaecides commonly used in lakes and ponds. It is safe to use according to the label for all types of algae control in natural ponds, but restrictions concerning fish harvest apply. This type of treatment works well with aeration to combat the negative effects of the algae die off.  Proper calculations and measurements of your lake or pond are critical in making these applications.  Misapplications can lead to no effect or negative effects, such as a fish kill.  Blue Ridge Wildlife & Pest Management, LLC is a licensed certified aquatic pest control company in Virginia and can effectively make this application to your lake or pond.

Virginia Aquatic Weed Control - Algae - Physical / Mechanical Treatments

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Physically Removing Algae : This method is used for filamentous algae and erect algae and is very labor intensive. The benefit to this approach is that you remove nutrients with the plants which gets the fertilizers out of the water to temporarily stop the cycle of growth. People have used dip nets, rakes, pulled by hand, etc.

Virginia Aquatic Weed Control - Algae - Aeration

Toll Free 855-WILDPRO (945-3776)

Adding a Pond Aerator, Aerating Fountain, or Water Circulator will help add oxygen and surface agitation to your lake or pond and will help with algae problems. However, aeration and water movement are not cure-all's or silver bullets for algae or water quality problems. As with many things in life, it is all about balance and working with other items that produces the best results. There are several available methods for algae control and prevention, such as herbicides, bacteria and microbes, chemicals, and UV sterilizers. Each has a slightly different way of attacking algae and some may work better in different situations and applications. However, each is designed to help eliminate and prevent algae from growing. Some only treat one generation of algae blooms, others may work for a longer period of time. Either way, when the algae dies off from natural causes or from one of the above treatment methods, there will be a large oxygen demand and Aeration can help. Also, the added water movement and mixing helps evenly distribute the treatments used and often makes the treatment work more effectively. 

Virginia Aquatic Weed Control - Algae

Toll Free 855-WILDPRO (945-3776)

Algae is often a catch-all for all aquatic plants and aquatic plant related problems. This page separates the two for this reason. Not all aquatic plants are algae. Also, not all algae is created equal when it comes to how desirable or undesirable it is in your pond.

Part of the reason many call all aquatic plants algae is because even experts differ on what to call or classify algae. Defining algae is very difficult, but basically, algae is a simple organism that lacks a true supporting or conducting tissues that the vascular flowering aquatic plants have.  Algae do not produce true roots, leaves, or flowers.  These tiny plants will float or attach themselves to underwater surfaces in your lake or pond and as the weather becomes warmer the plants will rapidly multiply.  There are three basic types of algae, planktonic, filamentous, and macrophytic.

Planktonic algae are single-celled, microscopic plants which are distributed worldwide. Blooms can be bright green, pea soup looking or even a blood red color. They are the base of the food chain and a healthy existing pond or well prepped new pond must have planktonic algae as a food source. 

Filamentous algae are called many things such as pond scum or moss, and they are typically found at the surface in the form of greenish mats. Typical growth begins on the edges of ponds and will slowly rise until it arrives at the surface. This series of cells joined together has a slimy, cottony or course texture. It can look like the stringy mass or it can be "scum" or a green mat on the water surface. Filamentous algae will grow in ponds with higher levels of calcium and phosphorus. It is common to have this type of algae encouraged after ponds are limed to enhance fish production. Filamentous algae typically are of little or no value to you or your pond.

Macrophytic are non-rooted but dense. A misconception is that it looks like a vascular plant, which causes a lot of confusion because they attach to the bottom like a rooted plant. There are two species of marophytic algae that are native in Virginia.  Muskgrass (Chara) and stonewort (Nitella). Both grow submerged usually in clear water.  Chara has a musky garlic like odor when crushed and has a gritty texture to it.  Nitella is smooth and delicate without any odor when crushed.

Problems with Algae

Often the most frequent complaint about algae is aesthetics. A green pond covered with algae is unsightly and is an eye sore. The enjoyment of the pond or water feature is diminished when algae has taken over.

Algae pose a problem to your lake or pond health when you have too much algae and during algae blooms. During the photosynthesis process when plants use sunlight and carbon dioxide to produce food, they give off oxygen. Photosynthesis is a good process for your pond. The plants are using carbon dioxide and giving off oxygen which is needed for your fish, the decomposition of organic matter, and other processes within your pond. However, photosynthesis only occurs when there is sunlight. As the sun goes down, plants turn from oxygen producing organisms to oxygen consuming organisms. Therefore, the more aquatic plants and algae you have in the pond or body of water, the more oxygen they will give off during the day and the more they will consume during the nighttime hours. As the night goes on, the oxygen levels continue to decrease. The lowest levels of oxygen will be just before sunlight in the morning before the algae and plants start producing oxygen again. If your pond has too much plant life, the oxygen levels can decrease to the point that large fish struggle to live.

An algae bloom is a rapid reproduction and spreading of algae when conditions are right. Algae blooms typically occur during the hot, sunny, calm part of the summer. When an algae bloom occurs, your pond can be covered with algae in a very short period of time. The major problem with an algae bloom is the algae die off. Often even quicker than the bloom itself, the algae die off can create major problems. A die off of an algae bloom can be caused by a cloudy day and lack of sunlight, a cold front, storms, etc.

When the algae bloom dies off, it adds a large amount of dead organic matter to your pond. This organic matter is decomposed by microorganisms at the pond bottom. With the added organic matter load on the pond, the total amount of decomposition occurring in the pond increases and the decomposition process uses up oxygen and gives off carbon dioxide.

This causes two problems. The first is lack of oxygen. When the oxygen in the pond is used to decompose the dead algae, it is not available for fish and other aquatic life. A die off can be so severe that most of the available oxygen in a pond can be used up in the decomposition process and your fish and other aquatic life will start to die off. The larger the organism, the more oxygen it uses. Therefore, your larger fish that have been in your pond for several years will be the first to die when oxygen is taken up.

The second problem with a large die off and increased organic matter is nutrients. When the algae die off and are decomposed the carbon dioxide and nutrients are released back into the pond.  In turn the nutrients become available for the next generation of plant material. The carbon dioxide and nutrients help to begin the cycle all over again.

Excessive algae growth will also limit sunlight from penetrating your pond and can cause significant thermal stratification, which is temperature layers throughout the pond. The water that does not receive the sunlight and warmth cools and becomes more dense. This dense water sinks and oxygen levels decrease because it is not in contact with the air. It can also cause turnover in fall and spring, which is discussed in more detail in the Temperature Solutions page.

Benefits of Algae

Algae in general serve a purpose and are essential for a healthy pond. Planktonic algae is the first link in most food chains that occur in your pond and your pond ecosystem needs algae. Zooplankton feed on planktonic algae and bait fish and fingerling sport fish in turn feed on the zooplankton. Without a food source, the bait fish and fingerlings will struggle and not thrive in your pond. Often times, pond owners who are managing their pond for trophy bass production will fertilize their ponds to keep the planktonic algae population very high. This serves to provide more food for zooplankton, bait fish and fingerlings and also blocks much of the sunlight from reaching the bottom of the pond. In turn, other aquatic plants struggle which decreases the areas for bait fish to hide and gives the bass a much easier meal to come by.

True Cause of Pond Problems

With all of this said, algae or aquatic plants are not the problem with the pond, they are simply a symptom. Nutrients are the main problem with most ponds. The main reason for any algae or aquatic plant problem is there are too many available nutrients in the water for the plants to grow and thrive. Grass clippings, leaves, runoff from fertilized lawns and farm fields or pastures, animal waste (from geese, ducks, fish, etc.), and organic matter in the pond (dead aquatic plants) are some of the most common sources of nutrients in ponds. All of these supply an enormous amount of nitrogen and phosphorous that aquatic plants and algae need to survive and thrive. The key to algae and aquatic plant control is controlling the amount of nutrients entering and existing in the pond.

Limiting the nutrients is easier said than done. More detailed information can be seen in the Nutrient Problems page, but physically blocking nutrients from entering the water is a first step. The second is helping remove the nutrients that are already in the pond. This can consist of physically removing aquatic plants by cutting or raking them out of the water. All the organic matter in the pond has nutrients in it and when it dies, it will release those nutrients that will be available for others in the future. Simply killing the plants doesn't do much for the overall problem, they need to be removed. The third step is to add aeration. The extra oxygen, as stated earlier, will help the decomposition process occur faster and will help limit the amount of nutrients available. Also, the aeration will help vent some of the gases like carbon dioxide and others that contain nutrients that plants need to survive.

Kasco aeration products, such as the Pond Aerators, Aerating Fountains, or Water Circulators are one piece of the algae solution, but a major piece at that. By adding oxygen and surface agitation, an aeration product can help prevent a major algae problem, help reduce the effects of an algae bloom and die off, and over time help limit and remove the root of the problem, which is too many nutrients in the water.  Aeration may not be a cure-all or a silver bullet for your algae problem, but it will be a big first step forward in the fight to either reclaim your existing pond or protect your new pond.


Southern & Southwest Virginia

Blue Ridge Wildlife & Pest Management, LLC
Wildlife & Fisheries Biologists on Staff
Roanoke, Bedford, Blacksburg, Covington, Radford, Smith Mountain Lake Areas
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Tidewater Wildlife & Pest Management, LLC
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Chesapeake, Hampton, Newport News, Sufolk, Virginia Beach, Williamsburg, Yorktown Areas

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