Lake Weed Control Advice


Aquatic weed control can be practiced in several ways, of which, the very best is lake weed prevention. Chemical control relies on herbicides to accomplish the job of vegetation control. Mechanical aquatic vegetation control is the act of physical weed removal, and is used generically for almost any time of physical lake weed control such as mowing, or rolling the vegetation. Biological lake weed control is accomplished by introducing a living predator into the pond or lake. These are limited at this time to a very few, including grass carp, and a few insects. As we said, prevention is the best method, and the follow up process is important for preventing future invasions.

Lake weed prevention.

Prevention is the best from of control for any problem, ever. However, there are times when prevention may not have been an option, and for such cases, exercising control, or practicing management is the only recourse.

Chemical lake weed control

Chemical aquatic weed control is often seen as being the least acceptable form of aquatic weed control due to environmental concerns. These concerns are largely unfounded. The amount of chemical that can legally be used is most often measured in parts per million, and relatively few parts per million at that. The chemicals used have been thoroughly tested, and while most of us have a healthy distrust of both government agencies and chemical manufacturers, I believe that in this case, they have earned our trust. The chemicals that are used for aquatic vegetation control are low dose, low toxicity, and lose their toxicity quickly in lake and pond water. You probably get more parts per million of pharmaceuticals in your drinking water than the allowable amounts of weed killers in fish ponds!

Chemical applications and "fish kill"

Occasionally we hear of someone treating a pond or lake and killing all the fish. This is a rarity, but it has happened. In all cases of which I am aware, the chemicals played only an indirect part in the problem to the extent that the chemicals did what they were designed to do but the lake manager killed off too much vegetation at one time, and the rotting vegetation used all the available oxygen, the fish died of oxygen depletion. Don't be afraid of chemical lake weed killers, just be certain that you use them properly.

Mechanical lake weed control

Mechanical aquatic weed control can be a good way to control aquatic weeds, but like other methods, it comes with a price tag.  It is usually a last ditch effort which will result in the continued need of the process.

Lake weed reproduction and fragmentation

Aggressive aquatic weeds like Hydrilla can reproduce from vegetation fragments  at a rate of  50 percent or more. This means that if your mechanical harvesting method shatters the weed into 200 pieces, and only 100 of the pieces are retrieved, you will have created about fifty more new plants! The trick to effective mechanical lake or pond weed control is to cause as little fragmentation as possible, and collect all the fragments. Machines with serious vibration, or machines that tear, rip or shred weeds should be avoided unless you are willing to seine the lake completely a time or two.

Mechanical weed control equipment

There are a few pieces of equipment I can recommend if this is the route that you intend to try. Email me for the details. Just beware that a commitment to mowing your pond or lake once, probably translates into the need to mow your pond or lake on a regular basis just as you mow your lawn.

Biological lake weed control

Biological aquatic weed control is one of the most difficult control measures to get right. The few biological methods for weed control come with a caution. Biological controls of this type usually require the introduction of a new species into the habitat. This would normally be one of the predators from the same location as the weeds you are attempting to rid yourself of. You will then have 2 exotic species in the habitat! There are many control measures exercised before the approval of a biological control, and they work pretty well under normal circumstances, but nothing in nature is static, and serious consequences are a possibility. As of this time, biological aquatic weed control seems to be limited to one oriental fish, and a few insects.

Lake vegetation control follow up

Please be aware, that any of these treatment methods are only effective for the amount of time that it takes the weeds to regain their growth unless something else is done. Action must be taken to prevent sunlight from reaching the bottom of the lake to prevent regrowth. If these measures are not used, and the proper steps are not taken, the problem will return! For information on pond scum prevention and control see: Pond Scum Control Advice For a paid consultation about dealing with your aquatic weed and pond scum problem see:

Lake Consultation

Pond Scum Control Advice


Filamentous algae, otherwise known as pond scum, is a nightmare for many pond and lake owners. The pond scum problem has a lot in common with other types of lake vegetation problems, and the cure for one will probably cure both. So, how do you get rid of pond scum? There are a number of different treatments, but the best method for dealing with pond scum is to prevent it from starting, and the method of prevention may come as a bit of a surprise.

Pond scum treatment

Pond scum, no matter where it ends up, starts at the bottom of the pond or lake. Pond scum is noticed most often on the surface of the lake or pond, but like emergent, or submersed lake weeds, it has its start on the lake bed. Pond scum treatments usually involve the use of a copper substance in liquid or granular form, or a contact weed killer like diquat. These products kill the algae, by punching tiny chemical holes in it, and the pond scum loses it's buoyancy and drops to the bottom. If you have this problem over a good portion of the lake or pond, it is best to treat only one third to one half of the lake at a time because the rotting vegetation requires oxygen to decompose, and it will take it from the water, which leaves less oxygen for your fish.

Pond scum removal

It is possible to physically remove pond scum from the surface of the water, but this process involves a good deal of manual labor in either skimming, or raking it. If you use copper sulfate or one of the other commercial herbicides labeled for pond scum or blanket weed control the algae will turn brown and sink to the bottom where it will degrade on it's own. Be aware that if you do not perform proper follow up procedures, the filamentous pond algae will return! Treatments of this type are sometimes needed, but such pond treatments are like the emergency room doctor after an auto accident. We are glad that he is there, but, it would have been better to have avoided the accident to begin with.

Preventing pond scum

Pond scum starts at the lake or pond bottom, it begins when sunlight penetrates to the bottom. Preventing light from reaching the bottom will prevent pond scum in the majority of cases. The prevention of pond scum, like the prevention of lake weeds requires doing something that will keep sunlight from reaching the lake bed. This involves water depth, and water clarity.

Adjusting water depth

There are two ways to change water depth. Raise the water level by adding water and maintaining it at a higher level, or removing soil from the bottom.

Raising the water level

Any attempt to raise the level of a spillway or overflow pipe should be preceded a thorough inspection  of the lake by someone who has the expertise to determine the success of such a project.

Removing soil from the lake bed

The other method for adjusting the depth of water in a pond or lake is to remove soil from the lake. This dredging process can be accomplished by draining the body of water and using earth moving equipment  to remove sediments, or by leaving the water, and hiring someone with specialized equipment built for the purpose. Either way, the project will be costly and time consuming. Ideally, there should be no area of the lake or pond that is less than 3 feet deep.

Adjusting water color

If water is too clear, then enough light can penetrate to produce filamentous algae. If sunlight can penetrate more than 24 inches, the water is too clear. There are colorants available which can do the job, but such colorants interfere with the natural food chain in the lake. The best means of producing color in a pond or lake is with tiny single cell algae known as plankton. Producing an "algae bloom" will reduce the depth to which sunlight can penetrate water, and prevent pond scum from becoming a problem. This is something that should be done even if your pond or lake is deep enough already. It will encourage the food chain and provide more healthy fish for your recreational fishing and for the table.

How to produce algae bloom

To start algae bloom, all that needs to be done is to add the proper amount of the proper fertilizer to the water. This should be done only after testing the water for proper pH, and amending the pH if needed. Once this is done, and the fertilizer added, the reaction will be swift. This should be followed by regular applications at 2 week intervals, and water clarity should be tested to be sure that it is working, and that water clarity is no more than 24 inches, and no less than 12 inches. If secchi depth is less than 10 to 12 inches, skip the next fertilizer application and re check the clarity periodically until it gets into the acceptable range before re starting the program.

Natural pond scum prevention with barley straw

There is evidence that pond scum can be prevented by using barley straw. The straw is submerged, or partially submerged in the water, and the decaying barley straw produces some chemical reaction that is not yet fully understood, but which seems to discourage filamentous algae production. It should be stated again, that this is not a treatment for existing pond scum, but another tool in our pond scum prevention kit. Remember that any algaecide, including barley straw is indiscriminate in pond algae destruction. When the pond scum is destroyed, there is a good chance that it will destroy the beneficial pond algae as well. Follow up is essential for for healthy ponds and lakes. For a paid consultation about dealing with your pond scum problem see:

Lake Consultation

Lake Weed Prevention Advice


Lake and pond managers and owners spend a good deal of time and money dealing with lake weeds. In fact, it is fair to say, that dealing with aquatic weeds is where the lions share of pond and lake management time and money is spent.

Exotic lake weeds

Lake weeds are an ever increasing problem today, in large part, because of the presence of so many exotic weeds, and their amazing and terrible growth habits in our climate. A plant that may have been a beautiful and productive part of it's native landscape in another region of the world can become a destructive lake eating monster when transplanted into a new environment. Unfortunately that is what we are experiencing in the Southern United States.

Native lake weeds

As bad and difficult to deal with as exotic lake weeds are, they are not the only weed problem that lake managers deal with. Our native varieties can be devastating if conditions exist which encourage their excessive growth. Native aquatic weeds can become almost as problematic as exotic aquatic weeds.

Preventing lake weeds

Lake weed control can be difficult and expensive. Every treatment option has it's drawbacks, some are like the medications advertised on television that have side effects worse than the original problem. In fact, there are no good or great treatment options, because they all deal with the symptoms and not the problem. There is a better way. When dealing with lake weeds, we can think of the process as a series of steps, with the best options at the beginning, and the least desirable options left to the end as a fall back position. The best option is prevention. Stopping lake weeds before they get a start is better than dealing with lake weeds after they have become a problem, in the same way that avoiding auto accidents and house fires is better than the very best methods of dealing with the aftermath. Prevention is always better than treatment.

Keeping lake weeds out

It is obvious that if there are no invasive lake weeds introduced into the lake, there will be no problem with them. So how do the lake weeds get into the lake to begin with?

Natural elements you can't do much about

The processes that bring invasive lake weeds into a body of water can be natural, such as birds and animals, or overflow from infested ponds or lakes upstream. This can be unpredictable, and unpreventable, but luckily, this is not the most common means of aquatic weed trans-location.

Human elements you can do something about

By far, the most common means of aquatic weed movement is human beings. This is usually done with boats that have not been cleaned properly after visiting another lake, or fishing equipment that has small pieces of plants that go unnoticed, and even by recreational equipment like all terrain vehicles. If living tissue from some exotic lake weeds from any source makes it's way into your lake or pond, it can, and probably will start to grow, and that growth may be geometric! If you are ever going to become an advocate of clinical cleanliness, this is the place to do it! Check everything that goes in or near the water. Leave no stone unturned when it comes to clean up, check live wells, bilge, propellars, everything! Check lures, nets and anything else that might hold a fragment, because a fragment of some exotic lake weeds can become a lake full  in just a few weeks!

Proactive lake weed prevention

The next step has elements of both treatment and prevention. It involves making your lake less vulnerable to lake weed infestation by strengthening it's defenses. Ideally, your lake or pond should have no areas under 3 feet in depth. This depth will control the majority of the lake weeds we consider problematic. In 3 feet of water, it is difficult for light to reach the bottom, and that is where most weed problems begin Unfortunately, most ponds and lakes are just not built this way, and even if they were, sediment gradually accumulates around the edges. Raising the water level can be unsafe if the dam is not strong enough and high enough to hold, and dredging can be very expensive. Whether you have shallow spots or not, there is another approach that you should consider, in fact, this should be done whether you have problems with lake weeds or not.

Water color

If your lake has clear water to a depth of more than 24 inches, your fish are probably hungry, and you probably have a problem with lake weeds and pond scum. Tinting the water will prevent the sunlight from penetrating to the bottom, and will, thereby, prevent the majority of submersed, and emergent lake weeds. How you tint the water will determine whether or not you have skinny fish!

Algae bloom

There are colorants on the market that do a good job of preventing light. They serve a useful purpose in many cases, but not when it comes to ponds and lakes used for recreational fishing. In such cases, what is needed is plankton, or non connected single cell algae. Plankton is the natural colorant for ponds and lakes, and it is the natural food for the microscopic aquatic life which feed the bugs, which feed your fish. Algae bloom is the beginning of the life cycle in lakes. The great thing about this is that it is easy to produce. If all other conditions are right, a relatively small amount of fertilizer can start the process in a matter of days, or even hours. For lake weed control methods see: Lake Weed Control Advice For a paid consultation about dealing with your pond scum problem see:

Lake Consultation

Lake Advice And Consultation


Lake Advice is an advice and consultation service for property owners who have pond and lake problems, from an experienced pond and lake manager, and lake weed control specialist. We offer basic pond and lake care information on the website, and consultation via phone and email.

Why are we offering this service?

There are many reasons. We have found that pond and lake owners, like everyone else, want to spend as little money as possible on maintaining their lakes and ponds. This is understandable and we respect this concern. Hiring a lake manager, or lake weed control specialist can be an expensive proposition.

The high price tag is a result of a combination of factors:

  • The high cost of chemicals and equipment used for lake management and lake weed control.
  • The difficulty of becoming a licensed aquatic vegetation manager.
  • The high cost of maintaining the license and insurance necessary for the job.
  • The limited numbers of available jobs in the market, and the uncertainty of when the next job will arrive forces a slightly higher labor cost.

There are factors that add to the degree of difficulty in this line of work:

The degree of uncertainty involved in practicing lake weed control when so many factors are beyond the control of the lake professional can be a problem. Weather factors, and human factors can negate the results of  a good application. The reluctance of many lake owners to perform the follow up needed to maintain the body of water after an application has been made can lead to problems as well. In many cases, the best proposal is for the property owners to perform the work for themselves. The advice offered on this site is for just such a situation. It should be remembered that the advice offered here is just basic advice. For more detailed help we offer online consultation for a reasonable fee.