How Can I Keep Lake Weeds From Taking Over My Pond?

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The best control is prevention. Preventing lake weeds from infesting your pond or lake is the single most important part of lake weed control. The methods are simple, and straightforward. One is a matter of vigilance, and the other a matter of good management practices. Most of our lake weed problems are with weeds that are not native to our area, therefore, the best method of controling them by prevention is to avoid introducing them into your pond or lake. Prevent non native lake weed problems through vigilance This is a simple matter of making sure that anything that might have been in an infested pond or lake does not make it into your reservoir without a good inspectin and cleaning. This includes boats and fishing tackle, trailers and anything else that went into or near the water. Sometimes animals, and even runoff from other water bodies may be a problem. There is not a lot you can do about natural causes, but they account for only a very small fraction of invasive lake weeds. Most lake infestations come from human carelessness. Lake weed prevention through good management Have you ever noticed how lake weeds start in the shallows? There is a reason. It is because light can reach the bottom. Lake weeds cannot grow without sunlight. It is as simple as that. If you can prevent the sunlight from reaching a depth of more than about 20 inches, you may still have problems in areas that are very shallow, but you will be able to prevent lake weeds from starting in other areas. The method is pretty simple. Here are the steps:
  1. Determine the pH. I put this first, because it is something you should do to make the rest of this exercise success. It should be between 6.8, and 8.6. If it is not, correct it by using lime as described in the lake weed control section of this site.
  2. Determine sechi depth. This is the depth that light can penetrate water. This will tell you what your next step should be. If the sechi depth is under 1 foot, your lake is too fertile, and you need to do something to reduce it's fertility, like planting a vegetative barrier, reducing fertilization around the surrounding area, or increasing water exchange. You can find the answers you need in this section.
  3. Fertilization. If the depth is more than 24 inches, you need to fertilize. Fertility will cause algae bloom, which will result in reduction of light penetration, which will reduce the chances that lake weeds will spring up. The information you need to accomplish this can be found here.
Follow these steps, and you may not avoid all your lake weed problems, but you will reduce them to a manageable level. Remember, You do not want to eliminate all vegetation, just the non native invasives, and excessive natives. About 20% of your lake area should contain vegetation.

Lake Weed Control: The Best Method

The best lake weed control is smart cultural practices

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  • The best lake weed control is not aquatic herbicides or lake weed killers.
  • The best lake weed control is not with mechanical harvesting devices or lake weed cutters.
  • The best lake weed control is not with hand cutters and rakes.
  • The best lake weed control is not with biological controls like Asian fish and strange foreign beetles.

Lake weed prevention

The very best lake weed control is to never give them a chance to become a problem in the first place! The best lake weed control, like the best disease control, or the best fire control, is prevention!

How do you prevent lake weeds? Simple, do not give them a start, and do not give them a place to start. If you never allow the introduction of exotic lake weeds, you will never have an exotic lake weed problem. Other types of lake weeds may grow naturally in your area, and that is where the “not giving them a place to start” part comes in. I am not talking about getting rid of your pond or lake, but about getting rid of the conditions which favor a lake weed control disaster.

Lake, lake weeds, lake environment

For any organism to take hold, it must first have a host, and second, a proper environment. If the environment is unfavorable, or no organism or host present, the chance of having a serious problem is just not present either. Think of your pond or lake as the host, lake weeds as the organism, and the condition of your pond as the environment. Obviously you don’t want to do away with the host, that is your lake. The organism, that is, the lake weeds are ever present, so you can’t do much about that, the only thing left is to deal with the environment, that is, the conditions of the pond or lake.

Modify the lake environment

Your goal as a pond or lake manager practicing preventive lake weed control, is to modify the lakes environment to favor the health of the lake, and to help it to become resistant to the invading weeds. This is done by using good cultural practices.

Lake fertility

Lake weed control problems are a result of one of two things. Either the lake is overly fertile, and the weeds emerge as a result of the excessive fertility, or the lake is under fertilized, and the weeds grow as a result of the lake beds exposure to sunlight. In both cases, shallow water is usually a factor. Fertility, out of balance, is always a potential problem. In the majority of cases, lack of fertility is the problem.

Why is this? When sunlight reaches the bed of a pond or lake, it warms the soil, and activates photosynthesis in plant life existing in a more or less dormant stage. This encourages growth. If sunlight does not reach the bottom, growth is prevented. Pond fertility, when in balance, produces phytoplankton which shades the bottom by coloring the water.

To solve the lake weed problem, to prevent it from recurring, the fertility must be kept in balance. Monitoring and maintaining lake fertility is the primary tool for lake weed prevention.

See also: How To Fertilize A Pond Or Lake

Pond Scum And Lake Weeds The Real Problem

Part 4 in our series on lake and pond interactions

The real pond scum and lake weed problem


The problem is sunlight. You can’t do much about that. Specifically, the problem is sunlight reaching the pond bottom, which you can do something about! The common issue for pond scum and lake weeds is sunlight penetrating the water to the bottom of the pond or lake. When this happens, a process begins which will allow lake weeds to grow unchecked, pond scum to develop and start to rise to the top, and the secondary result will be mosquitoes, and even though the plants and algae will produce oxygen, they will at some point cause conditions which will deplete oxygen in the water, and all the while, your fish will be starving. All of this because sunlight reaches the pond bottom!

Preventing lake weeds and pond scum by preventing light penetration

There are a number of ways to prevent light from reaching a pond or lake bottom. You can raise the water level, lower the bottom through dredging, or color the water in some way. Raising the water level can produce good results in some cases, but may not be practical, and it still doesn’t deal with the issue of skinny fish. If the water is deep enough the sunlight cannot penetrate, but something needs to be done to feed the fish if the water is clear to a depth of more than 24 inches, so even if you can raise the water level, or dredge the shallow areas, more is needed. The water needs color to shade the bottom. This can be done with dyes and colorants, but, once again, you still have the issue of skinny fish. There is a product that can resolve both the light penetration issue, and the food supply issue.


Plankton is a single cell algae which is suspended in the water of healthy ponds and lakes. It provides oxygen to the water, food for the tiny invertebrates that feed the larger aquatic life, which ultimately feeds the fish in the lake, and provides color for the water helping to prevent the excessive growth of unwanted vegetation and pond scum. This is sometimes called algae bloom.

Producing algae bloom

The reason that plankton does not grow in a pond or lake is lack of fertility. The solution to this problem is to add fertilizer. To learn more about this process see: pond scum prevention and Lake weed prevention Pond scum is filamentous algae, and is also known as blanket weed, pond blanket weed, and a few, less desirable terms.

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