Algae and Aquatic Weed Control
Aquatic weeds and algae present a constant challenge in pond maintenance. The amount of aquatic vegetation growth is a function of water depth, water clarity, weather patterns, and nutrient loading. In addition to being an eyesore, algae clog filters, pump inlets, and other equipment. Sedimentation is accelerated, oxygen levels reduced, and bad odors result. The pond's use and state regulations influence the treatments selected. Aquatic plant management should be a combination of methods that work harmoniously with the environment. There many techniques that help maintain the pond environment. These include pond aeration, filters, controlling runoff, biological methods, and the use of aquatic algaecides and herbicides. Some plant growth is a viable part of any aquatic ecosystem but excessive plant growth soon becomes an undesirable weed population that requires treatment and control. Proper identification of plants is critical to the treatment process. Many herbicides are selective and are only effective on specific types or species of plants. On our “links page” we have included several links to weed identification web sites and links to the various algaecide and herbicide labels that are mentioned in this chapter. This chapter will give you an overview of the various types of weeds and algae, plus a general overview of the best products to use in your chemical treatment program.
There are five major groups of aquatic plants. They are classified as algae, marginal, submersed, emersed, and floating.
Algae; Fresh water algae is very diverse in shape, color, size and habitat. To describe all species of algae we would need to write a paper that would equal descriptions of all land plants, mosses, ferns, fungi, and seed plants combined. All forms of algae contain the green pigment chlorophyll, but the green color can be masked by other colors including red, brown, blue-green, and black. Algae are often the primary food source for an aquatic environment and are an important producer of oxygen, even under the ice in the winter. Algae can also be the primary problem in a pond and is often difficult to correct. There are three major groups of algae.
Planktonic algae or 'pea soup' algae; this group is also called phytoplankton to separate it from the microscopic animal forms called zooplankton. These are microscopic plants that suspend in the upper few feet of the water. These algae can rapidly become a heavy bloom that covers an entire pond with green or brownish scum. Planktonic algae are the most easily controlled with copper compounds but treatments must be applied before this algae reaches the stage of a heavy bloom. Blooms will often use up all available nutrients and die off suddenly causing a serve oxygen drop from decomposition of dead algae. Certain species of Planktonic algae can product toxic substances which are stored in the cells and are released as the cells die. This will poison the water to pets, livestock, wildlife and fish. The addition of supplemental bacteria will help control Planktonic algae by depriving it of nutrient, stopping this problem before an algae bloom begins.
Filamentous algae, called moss, blanket weed or horsehair clump; Filamentous algae is a chain of identical cells that grow lengthwise at the tips forming free floating filaments. This form usually reproduces by fragmentation. These mats of algae product large amounts of oxygen that gets trapped within the filaments, which causes the mats to rise in the water and float free on the surface causing the algae to spread to other areas of the pond. These free floating clumps also clog pump intakes and foul irrigation lines if the pond water is used in an irrigation system. Applying Aqua Doc microbial treatment along pond edges will help stop filamentous algae from developing by reducing nutrient and biomass along the pond edge.
Chara, also called muskgrass; is called attached-erect algae that has a weed-like appearance and is anchored in the pond bottom completely underwater. This type of algae looks like weeds growing on the pond bottom but there are no roots or vascular system since the plant is actually a form of algae. The best way to identify this type of algae from other aquatic weeds is by its musky smell and gritty feel. This is due to calcium deposits on the surface. These calcium deposits make the plant resistant to chemical treatments in the later season and it's best to begin treatments in the early spring. The water tends to be very clear when Chara is present.
Types of aquatic plants: Most species of aquatic plants are found across a wide spectrum of freshwater environments and have wide ranges, often worldwide. Each species of plant plays a role in the ecology of the system. The essential function of aquatic plants includes the following: they produce oxygen to aerate the water (from photosynthesis), provide shelter for fish and freshwater invertebrates, consolidate the pond bed and banks, provide food for aquatic organisms, and a spawning medium for many fish. Marginal plants provide nesting sites and a food source for waterfowl, as well as provide aesthetic appeal to the ponds.
Marginal Weeds- Plants that grow in the saturated soil on the waters edge, like cattails.
Submersed Weeds --True seed plants rooted on the bottom, mostly underwater with a few flowers above the surface like naiads.
Emersed Weeds- Rooted on the bottom with floating leaves and flowers, like arrowhead and waterwillow.
Floating Weeds-Free floating plants or rooted, but leaves rise and fall with water level, like duckweed and waterlilies.
You generally do not have a lot of control over the types of plants that will appear in your pond except for those you purposely plant. Mother Nature has a variety of ways of bringing algae and plants to your pond. Algae are very common organisms that can be found on land as well as in water. They are often the first occupants of your pond; aquatic plants come later. Seeds and fragments are brought in by the wind or on the feet of waterfowl. Plants and algae invited or not, will eventually find their way to your pond.
Before trying to rid your pond or lake of aquatic weeds, consider the benefits they provide to the aquatic environment. Maintaining a healthy balance of aquatic plants is critical to a pond's ecosystem. Aquatic plants provide the basic resources for the rest of the pond community and native aquatic plant communities help prevent the establishment of invasive exotic plants. It is rarely desirable to remove all the plants from a pond.
Komeen Aquatic Herbicide
(8% copper ethylene diamine complexes ) -a copper-based aquatic herbicide, usually has no restrictions such as buffer or setback zones, re-entry intervals or holding periods. Immediate access to water for drinking or recreational purposes is permitted after an application, so there's virtually no down time. Komeen's formulation gives fast uptake of any copper herbicide, effectiveness in hard water, a long shelf life, and the flexibility to use treated water on turf and ornamentals. Komeen can be used in golf, ornamental, fish, irrigation and fire ponds as well as fresh water lakes, fish hatcheries, potable water reservoirs, crop and non-crop irrigation systems.
This is a fairly broad spectrum herbicide; check the label for specific plants. Rates: Varies with depth of water. Example: In one foot of water, use 5 to 10 oz. per 1,000 sq. ft.
Glyphosate - (Trade names for aquatic products with glyphosate as the active ingredient include: Rodeo, AquaMaster, and AquaPro).
This systemic broad spectrum herbicide is used to control floating-leaved plants like water lilies and shoreline plants like purple loosestrife. It is generally applied as a liquid to the leaves. Glyphosate does not work on underwater plants such as Eurasian watermilfoil. Although glyphosate is a broad spectrum, non-selective herbicide, a good applicator can somewhat selectively remove targeted plants by focusing the spray only on the plants to be removed. Plants can take several weeks to die and a repeat application is often necessary to remove plants that were missed during the first application.
Fluridone - (Trade names for fluridone products include: Sonar and Avast!).
Fluridone is a slow-acting systemic herbicide used to control Eurasian watermilfoil and other underwater plants. It may be applied as a pellet or as a liquid. Fluridone can show good control of submersed plants where there is little water movement and an extended time for the treatment. Its use is most applicable to whole-lake or isolated bay treatments where dilution can be minimized. It is not effective for spot treatments of areas less than
five acres. It is slow-acting and may take six to twelve weeks before the dying plants fall to the sediment and decompose. 2,4-D - There are two formulations of 2,4-D approved for aquatic use. The granular formulation contains the low-volatile butoxy-ethyl-ester formulation of 2,4-D (Trade names include: AquaKleen and Navigate). The liquid formulation contains the dimethylamine salt of 2,4-D (Trade name - DMA*4IVM). 2,4-D is a relatively fast-acting, systemic, selective herbicide used for the control of Eurasian watermilfoil and other broad-leaved species. Both the granular and liquid formulations can be effective for spot treatment of Eurasian watermilfoil. 2,4-D has been shown to be selective to Eurasian watermilfoil when used at the labeled rate, leaving native aquatic species relatively unaffected.
Aquathol - Endothall
- Dipotassium Salt - Endothall is a fast-acting non-selective contact herbicide which destroys the vegetative part of the plant but generally does not kill the roots. Endothall may be applied in a granular or liquid form. Typically endothall compounds are used primarily for short term (one season) control of a variety of aquatic plants. However, there has been some recent research that indicates that when used in low concentrations, endothall can be used to selectively remove exotic weeds; leaving some native species unaffected. Because it is fast acting, endothall can be used to treat smaller areas effectively.
- The active ingredient in REWARD, diquat dibromide, has been used successfully without environmental concern for more than 25 years. When used according to label directions, REWARD poses virtually no environmental risks. Unlike some grounds maintenance herbicides, REWARD will not contaminate ground water. When applied, REWARD adsorbs quickly onto soil sediments, vegetation and organic matter, rendering it biologically unavailable. Because of its low application rates, REWARD is low in toxicity to fish and wildlife. Diquat is a fast-acting non-selective contact herbicide which destroys the vegetative part of the plant but does not kill the roots. It is applied as a liquid. Typically diquat is used primarily for short term (one season) control of a variety of submersed aquatic plants and algae. It is very fast-acting and is suitable for spot treatment and for shoreline algae growths. However, turbid water or dense algae blooms can interfere with its effectiveness.
- There are two formulations of triclopyr. The TEA formation of triclopyr is registered for use in aquatic or riparian environments. Triclopyr, applied as a liquid, is a relatively fast-acting, systemic, selective herbicide used for the control of Eurasian watermilfoil and other broad-leaved species such as purple loosestrife. Triclopyr can be effective for spot treatment of Eurasian watermilfoil and is relatively selective to Eurasian watermilfoil when used at the labeled rate. Many native aquatic species are unaffected by triclopyr. Triclopyr is very useful for purple loosestrife control since native grasses and sedges are unaffected by this herbicide.
-This systemic broad spectrum, slow-acting herbicide, applied as a liquid, is used to control emergent plants like spartina, reed canarygrass and phragmites and floating-leaved plants like water lilies. Imazapyr does not work on underwater plants such as Eurasian watermilfoil. Although imazapyr is a broad spectrum, non-selective herbicide, a good applicator can somewhat selectively remove targeted plants by focusing the spray only on the plants to be removed.
- Copper is an element used as an aquatic herbicide in several different formulations. All products have been used to control algae and other aquatic vegetation in slow-moving or quiescent bodies of water, including golf courses, ornamental fish and irrigation ponds, lakes and rivers.
Copper is naturally occurring and is found in soil and water often in the form of complexes, both organic and inorganic. Removal of elemental copper from an aqueous system occurs through binding to sediments and dissolved organic compounds. Many products containing copper are registered for use in most states, but some states have begun to restrict copper products because of the residual build up involved. Some algae may become resistant to copper with repeated applications.
Products containing copper sulfate include a variety of manufactures and product names (most of which contain 99% copper sulfate pentahydrate) and Earthtec (containing 20% copper sulfate pentahydrate). Other products contain copper complexes differing in the percent of copper as the active ingredient. These include Cutrine-Plus (9% copper ethanolamine complexes), Cutrine-Plus Granular (3.7% copper ethanolamine complexes), Lescocide-Plus Granular (3.7% copper ethanolamine complexes), K-TEA algaecide (8% copper triethanolamine complexes) and Komeen Aquatic Herbicide (8% copper ethylene diamine complexes).
These are product descriptions for some of these products; Copper Sulfate is a copper compound used for years as an algaecide. This product is used all forms of algae including: filamentous, planktonic, and branched algae. The crystal form is most effective on bottom mats while the fine crystal is broadcast over the treatment area or dissolved in water. Copper sulfate is less effective in hard water than chelated copper products. This product is corrosive to metal equipment and toxic to fish in soft water. Normal application rate is 2.7 pounds per acre foot of water treated. Effective for control of swimmers itch with special application methods. We feel Copper Sulfate is the least desirable choice of the copper based treatment products because of the draw backs that have been mentioned earlier.
If you find a copper algaecide that is working well in your pond, keep using it. You will begin know what to expect and when, where and how to apply. If you use a different product each time you treat, it is difficult to get any track record of the results for each treatment.
- (8% copper triethanolamine complexes) provides effective control of various filamentous, planktonic and branched algae which occur in quiescent bodies of water including golf courses, fresh water lakes, ponds and fish hatcheries. K-TEA is most effective when applied at the first signs of an algal bloom. K-TEA treated water can be used to irrigate crops, turf, fairways, putting greens and ornamental plants immediately after treatment. Application methods include aerial or ground spraying, spraying from a boat as a direct surface spray or direct subsurface application through weighted hoses.
-A 9% chelated copper algaecide for use in lakes, potable water reservoirs, farm ponds, fish and industrial ponds, fish hatcheries and raceways, crop and non-crop irrigation conveyance systems, ditches, canals, and laterals. Cutrine Plus under field conditions, is effective in controlling a broad range of algae including Chara, Spirogyra, Cladophora, Vaucheria, Ulothrix, Microcystis, and Oscillatoria. Effective in hard water. Treated water may be used for swimming, fishing, drinking, livestock watering, or irrigation immediately after treatment. Application rates range from 0.6 to 1.2 gallons per acre foot of water treated.
Cutrine Plus (Granular)-
A 3.7% granular chelated copper algaecide ideally suited for treatment of bottom growing algae including Chara and Nitella and spot treatments along docks, beaches, boat launches, and fishing areas. This formulation helps control growth before it reaches the surface. Cutrine Plus Granular is registered for use in lakes, potable water reservoirs, farm and fish ponds, fish hatcheries, and golf course water hazards. Treated water may be used for swimming, fishing, drinking, livestock watering, or irrigation immediately after treatment. Spread as evenly as possible over treatment area at a rate of 60 pounds per surface acre.
- This formulation has the same active chelated copper content as Cutrine Plus with the addition of a non-ionic surfactant. Cutrine Plus Ultra is more effective against hard to control algae.
The action of these products is very similar but the effectiveness of each product can vary with the water chemistry and the species of algae in each pond.
Other Types of Algaecides
is a granular peroxide based product. This product is new to the industry for the 2004 season and is not yet available in some states. The mode of action is oxidation, which provides immediate control of algae, and it releases oxygen as it works. GreenClean is one of the few non-copper based algaecides currently on the market. GreenClean can be applied by broadcasting, as a dissolved liquid, or as a subsurface application. Application rates range from 3-170 pounds per acre-foot depending on the amount of algae growth. Because of the method involved, this product is nonselective and will have an effect on all types of algae. Dead matter floats to the surface for removal. Once GreenClean kills algae, bacteria goes to work cleaning up organic material. GreenClean does not harm bacteria populations when used as directed.
-Endothall - Amine Salt - Hydrothol 191 is a rapidly acting non-selective contact herbicide or algaecide. Several treatments each season may be needed to control algae. Hydrothol 191® has a high acute toxicity to fish and must be used with extreme care. Unlike copper compounds that are also used for algae control, Hydrothol 191 does not accumulate in sediments and breaks down rapidly. There are water-use restrictions associated with the use of Hydrothol 191. Grass Carp may be killed by this product. Be very careful in it's use. Check the label for application rates.
We recommend that you work with as few of these products as is feasible in your situation. Most of these products have a broad spectrum of use and the affected plants overlap between products. As we've mentioned, the first thing you need to do is identify the aquatic plants you are trying to control. Next, check the product labels for these plants and algae, then select an algaecide or herbicide to address the problem. Using more than one chemical to treat the same problem is not always necessary or even a good idea. Many algaecides and herbicides can be tank-mixed and applied together as a chemical cocktail. The product labels give you directions on mixing rates, but don't use more chemicals that are necessary.
It is sometimes a better idea to try one treatment alone first. If you are treating for algae, select an algaecide that is labeled for that problem. Adding other chemicals makes it difficult to determine the effectiveness of the individual chemical. When you find an algaecide that is working well, stay with that product. The copper based products each have a different formulation and concentration so getting to know one product is better than using a different formulation each time you make a treatment. Many of the weed treatments cover the same plants, so try one to see what the results are before you add additional chemicals to the environment.
Dyes- Many brands of dye are available for lakes. In addition to adding a pleasant blue color these dyes can help to sun light inhibit photosynthesis and thus control some forms of weeds and algae. Most of these dyes are not registered with the EPA and do not require a chemical applicators permit. Aquashade is one dye that is both patented and registered by the E.P.A. for control of aquatic plant growth. Aquashade is a unique blend of blue and yellow dyes specifically designed to screen or shade portions of the sunlight spectrum required by underwater plant and algae growth. This shading inhibits photosynthesis in young, bottom growth suppressing growth and development of nuisance conditions. Dyes can be used in place of, or as a companion to, registered aquatic herbicides and algaecides in managing aquatic nuisance growth.
It is best to apply dyes before the growing season starts, or when growth is on the bottom. Application rates and the shade of color vary from product to product. This is one type of product where experimentation is a good idea. Each brand will be a different shade of blue and the look of the pond will vary by the brand you chose the results from dye can be seen right away so if you don't like the shade of one dye, try another brand next time you need to add color. We usually prefer to use dyes with a “true blue” color rather than dyes that add yellows or greens. While the addition of other color spectrums can be effective at inhibiting photosynthesis the actual look of the dye in the water is arguably not at nice as a simple blue color.
You should note that you probably won't need to add more dye more often than every 4 to 6 weeks and that using the full application rate suggested by many manufactures will give your pond a dark blue color. We recommend that you add only 1/3 the suggested rate per application until you reach the color intensity that looks best in your situation. Wait at least 2 days before adding more dye. You can always add more dye if you chose but you cannot remove it when you inadvertently use too much so start low and add more with discretion.
Muddy or cloudy water will change the appearance of the dye into a more brown or green look rather than the pleasant blue appearance you wanted when applying the dye. If your lake is turbid, wait on the dye until you can clear the lake up. Remember that your goal is to achieve a pleasant esthetic look to your pond and that too much dye might not help.
Here's some final notes on weed treatments. Aquatic herbicide application can be less expensive and more effective than manual or mechanical removal especially when used in controlling wide-spread infestations. Aquatic herbicides are easily applied around pump intakes and underwater obstructions. Some herbicides have swimming, drinking, fishing, irrigation, and water use restrictions (check the label). Non-targeted plants as well as the nuisance plants may be controlled or killed by some herbicides. Be very careful of back-spray onto terrestrial plants. Many aquatic herbicides will also kill plants and grass along the lake edge if not applied properly. Depending on the herbicide used, it may take several days to weeks, or several treatments during a growing season, before control is achieved. Rapid-acting herbicides like some copper formulations, endothall and diquat may cause low oxygen conditions to develop as plants decompose. Low oxygen can cause fish kills so make these applications on smaller areas with each treatment to avoid a major die-off at one time. To be most effective, generally herbicides need to be applied to rapidly growing plants, usually in the early part of the growing season. Some expertise in using herbicides is necessary in order to be successful and to avoid unwanted impacts. Chemical treatments should be done with planning and a degree of precision, more is not necessarily better for your ponds ecosystem.
Follow up any chemical treatments with applications of Aqua Doc Microbial treatment to stabilize the ecosystem and help mitigate some of the adverse affects of chemical use. It is usually advisable to wait one week after these treatments before applying Aqua Doc.
When you choose chemical herbicides, there are two different types of action: contact and systemic
. Contact herbicides achieve fast results, but may require multiple treatments during algae bloom season. Additionally, exposure of every part of the target plant is necessary. Systemic herbicides are slower to kill, however they often provide seasonal control, and there is less oxygen depletion due to rapid decomposition of vegetation. Only those chemicals registered with the U.S. EPA may be used. When controlling aquatic plants with chemicals, proper identification of the plants and the appropriate chemical for treatment is important
to be certain that treatment occurs at the proper timing and dosage. In order to apply chemicals in most states, the applicator must be licensed with the State. If you are a pond owner, it is probably best to contact a licensed applicator for these treatments.
Aquatic herbicides are chemicals specifically formulated for use in water to kill or control aquatic plants. Herbicides approved for aquatic use by the United States Environmental Protection Agency (EPA) have been reviewed and are considered compatible with the aquatic environment when used according to label directions. Many individual states also impose additional constraints on their use.
Aquatic herbicides can be sprayed directly onto floating or emergent aquatic plants or are applied to the water in a liquid or pellet form. Systemic herbicides are capable of killing the entire plant. Contact herbicides cause the parts of the plant in contact with the herbicide to die back. Non-selective, broad-spectrum herbicides will generally affect all plants that they come in contact with. Selective herbicides will affect only some plants (often dicots - broad leafed plants like Eurasian water milfoil, will be affected by selective herbicides whereas monocots like Brazilian elodea (Egeria densa) may not be affected). Most aquatic plants are monocots. This is the reason why proper weed identification and the appropriate chemical are so important. When we make general spot treatments to clean out an area of a pond we often use contact herbicides that will kill all the plants in the application area. By treating only a portion of the pond with each application, you can avoid the problems of oxygen depletion and excessive nutrient release. Applying Aqua Doc after these weed treatments will help remove the dead organic material in the system and control nutrient and sediment build up.
. This is a list and description of the most common herbicides and algaecides currently in use, some general information on each, and the types of plants each will control.
One point seems obvious but still needs mentioning; never attempt to control aquatic weeds by fertilizing the pond. There have been misconceptions for decades on the practice of pond fertilization. Before the plants become established, fertilization can promote microscopic algae, called plankton. As the planktonic algae grow they color the water green. At this stage they will help limit the depth of sunlight penetration and may limit the establishment of higher multicellular aquatic plants. This is not an acceptable method of weed control and will only serve to throw your pond in a eutrophic condition.
You have to decide the amount of aquatic plants you want in your pond or lake and the location where they will not affect the use of the pond, like interfering with golf ball removal or fishing in the pond. Not every aquatic plant becomes invasive where it will "take over" your pond. Some grow slowly and never become a problem. Because bass and bluegill have a preference for structure or cover, they will stay around the edges of your plants searching for food or seeking relief from direct sunlight in the shade the plants provide.
The first and most important step in controlling weeds and algae is proper identification. We have included several links to weed identification sites to help you with this task. See the Links section at the end of this paper or on our web site at
. The control method, products you chose, treatment method, application rates, expected results, and side affects to the ecosystem all depend on the type of plant present in your pond. Don't overlook this step.
Food and cover are closely related in aquatic habitats, providing cover generally increases fish food production
. There are two main types of aquatic cover - aquatic plants and hard cover such as logs, brush or large rocks. Aquatic plants are a necessary part of the pond environment and when controlled properly can be desirable; many are attractive and improve the aesthetics of a pond or lake
. Their role is important since only plants can convert solar energy into stored chemical energy for use by animals. Most insects used as food by fishes are herbivores - plant eaters - and require coarse organic matter for food. These insects feed directly on aquatic plants or on the microscopic plant and animal communities attached to plant surfaces.
Nearly all fish use aquatic insects as major food items sometime during their life cycle, so it is important to have an adequate supply for good fish growth. Aquatic plants are the habitat for many insects.
Aquatic plants also serve as escape cover for young fish and help prevent over-utilization of forage fish (usually bluegill) by predator fish (usually bass). Aquatic plants ensure that some forage fish can grow up to produce young and thus maintain a sufficient food supply for predator fish.
Ponds without adequate aquatic plant cover often develop a fish population composed of many small, slow-growing bass and a few large adult bluegills. In this situation, the few bluegills just can't produce enough young to satisfy the appetites of all the hungry bass. Many of the young bluegills that are produced are eaten as fry before they grow to a size that would promote growth of adult bass.
Aquatic plants help stabilize pond banks and shorelines, reducing wind and wave erosion. Severe erosion can muddy the water and greatly reduce productivity and fish growth. Emergent plants, like reeds and other shoreline plants provide important foods and nesting areas for waterfowl and shorebirds.
Good aquatic plant management is no accident; it must be planned. A rule of thumb is that about 15 to 20 percent of the surface area of a pond should have aquatic plant cover. The best approach is to have the plants interspersed with open water areas, rather than all in one spot. Using selected spot treatments with aquatic herbicides is the best way to achieve these results.
In general, there are four ways to control or remove aquatic plants. We will address the first three for reference but the focus of this discussion is on the chemical control method. SePRO Corp. the makers of SONAR, K-Tea and Komeen among other products, have a great, seven page PDF called,
Options for Aquatic Plant Management
, which does a good job of explaining pros and cons of alternative weed control options.
Manual/Mechanical: includes hand-pulling and raking or mechanically harvesting plants. Some States regulate these operations and a permit may be required.
Physical: includes bottom plant barriers and water drawdown. These methods are used only in special circumstances because they involve a placing structure on the bed of a lake and/or effect lake water level. Barriers are difficult to add to an existing lake and are generally reserved to new constructions.
Biological: includes herbivores and bacteria. Currently the most common biological controls are the stocking of grass carp, which will eat some varieties of aquatic weeds and the Galerucella beetle, which is used to control the exotic invasive plant Purple Loosestrife.
Adding supplemental bacteria will help reduce the bottom sediments in ponds and can reduce the growing area available to some aquatic plants.
Chemical: includes algaecides, herbicides and dyes. Chemical treatments can be the most difficult, costly and unpredictable part of a pond maintenance program. Chemical treatments to ponds usually require an applicators license in most states. The purpose of the license requirements is to make certain the applicator is properly trained and understands the legal and safety factors involved in using the products. We feel this understanding of the products and other factors is critical to the applicator. You should read the product labels carefully when deciding which treatments to make. It is also important for one individual to be responsible for the treatments to your pond. You need to become aware of the results of each treatment, positive or negative. Each pond is a unique ecosystem with unique water chemistry and aquatic life. This experience with the pond becomes an important tool to the pond-keeper in making ongoing treatment decisions to a dynamic environment.