How Can I Prevent Pond Algae?

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Not all algae is bad First, let's get our minds wrapped around this: Not all algea in ponds and lakes is bad. The problem comes when you have too much algae, or the wrong type of algae. In fact, the best treatment for pond algae, is algae! I know it sounds a little strange, but that is the way it works. What is pond algae When most people think of pond algae, they think of the type of algae commonly called pond scum, or blanket weed. The proper name for it is fillamentous algae. This is a type of algae that forms long fillaments or strings that then mat together to form a blanket on the surface of the water. This mat or blanket of algae makes fishing, boating, and other recreational use of a lake or pond difficult and distastefull. Pond scum also allows a perfect environment for mosquito production. In general, blanket weed in a lake is not a good thing for human use and interaction with the lake. Understanding pond algae To understand the best treatment for it, we need to understand where it starts, and how it starts. When we notice pond scum, we notice it on the top of the water, but that is not where it begins. Fillamentous algae starts at the bottom of your reservoir, and rises through the water profile as it gains bouyancy from the oxygen it produces. Eventually, enough oxygen is produced to lift it to the top of the water where it floats annoyingly. Clear water is the problem The problem is not that your pond or lake water is too murky, the proble m is that it is too clear. Again, I know that this is counter intuative, but bare with me. You have probably heard someone say "I can't see through muddy water." when they wanted you to move out of their line of site. The same principle applies here, because light penetrates straight through clear water, and because sunlight is needed for plant production, if the water is not clear, plant production is limited. If your water is too clear, you will have pond algae. The answer is not to go out and make the water muddy, the answer is to produce a single cell algae known as phytoplankton to tint the water, and prevent sunlight from reaching the bottom. So how do we prevent pond algae? Pond fertility is the answer. Check your pond or lakes water. If it is clear to a depth of more than 20 inches or so, it is too clear, and chances are, your fish are going hungry as well. A good fertilization program will solve both problems, and many others as well. This is how it works: When the proper amount of the proper fertilizer is introduced into the water, in the proper way, the single cell algae known as phytoplankton will reproduce rapidly in a process called algae bloom. This will continue as long as the water is fertile. The green color, or the golden brown coloring that this method produces will tint the water, preventing sunlight penetration, and preventing the growth of fillamentous algae. To learn how to do this see these pages, How To Fertilize A Pond Or Lake Lake Fertilization Lake Management Lake Weed Control Water Depth Secchi Depth and all the posts in this section of Home And Garden Press: Lake Management

Pond Water Color

Water coloring for weed and algae prevention

In order to prevent the growth of weeds and string algae, water in almost any type of pond or lake should not be perfectly clear. The way the water is colored is of major importance.

Clear water will not stay clear very long when exposed to the sun. Something will grow in the water, and it will probably not be what you want. To control this in farm ponds, fish ponds, lakes, or even in koi ponds and other backyard ponds, you will have to take some action. Prevention is better than trying to treat for slime, blanket weed, or submersed lake weeds later on. Getting out in front on this issue could save you a lot of money in treatment costs.

Pond water color good and bad

Not all pond water color is good. Turbid or muddy water isn’t good for any beneficial aquatic life, and the problem causing the turbidity should be solved before anything else can be done to improve water quality. This problem can occur for a variety of reasons, the most common of which is a bare watershed. Once the cause is dealt with, the water can be cleared using a flocking compound, and then the real work of getting the water properly tinted can begin.

The best pond water color is achieved with algae. Not string algae or pond scum, but the type of algae suspended in the water, known as phytoplankton.

Phytoplankton for pond water color

Phytoplankton is the best solution to most water clarity issues, it shades the water against sunlight, and uses nutrients which would otherwise be used by weeds and string algae, and it feeds zooplankton which feeds fish. There are several different types of phytoplankton.

Diatom algae

The type of phytoplankton present in the water is also important. There are many types, but perhaps the most productive is diatom plankton. These are the microscopic plants with silica exoskeletons which exist both in salt water and fresh water. Like phytoplankton in general, their numbers are diminishing, and have been for many years. Diatoms are very efficient in food production, and present a marked increase in zooplankton when they are present in large enough quantities. Diatom algae adds a golden brown tint to pond water.

Green algae

Green phytoplankton, have cellulose as their skeletons and produce increases zooplankton, but to a lesser degree than diatoms. Both produce color in the water, both remove excessive nutrients from the water, both produce oxygen, break down carbon dioxide, and raise dissolved oxygen levels, and both reduce weed and string algae production. Diatoms produce these desirable effects more efficiently, and great strides forward have been made in efficient means of producing it. Green phytoplankton produces similar results, but phosphorous is needed to produce and maintain this bloom, and phosphorus supplies are running low. Not all green algae are the same.

Dyes for pond water color

There are occasions where phytoplankton production may be difficult to acheive due to a variety of factors such as local water use restrictions. It is even possible to produce some types of fish without the presence of high concentrations of phytoplankton. Catfish respond well to regular feeding, and the introduction of fathead minnows into the environment, but for weed control, and for temperature control, some coloring of the water is needed. In such situations, and for decorative fish ponds, fountains, and other decorative garden type ponds, dyes may present the best possible alternative.

How The Parts Of Ponds And Lakes Interact


All of the parts of your pond or lake interact with all of the other parts. Each problem you have is a part of other problems, probably leading back to a single problem at some point. pH, lake fertility, dissolved oxygen levels, fish size and weight, and lake vegetation each have something to do with the other, therefore, it is important to trace any problem back through each factor, and find the primary cause. As an example, we have a 4 part series about how these interactions occur. Pond Scum Lake Weeds Mosquitoes And Skinny Fish Controlling pond scum, lake weeds and mosquitoes and raising healthy fish may seem complex and difficult. There is no miracle cure, there is no magic bullet. Pond Scum And Lake Weeds Most of the questions we receive about lake weeds revolve around how to get rid of them. As with pond scum, most lake weeds get their start at the bottom of the pond when sunlight reaches them. When conditions are right, they may grow out of control causing problems for the pond owner. Mosquitoes And Skinny Fish Mosquitoes on ponds and lakes may seem to be unrelated to lake weeds and filamentous algae. The truth however, is that mosquitoes become a problem when there is too much vegetation in the pond... If the water has too little of one type of algae, and too much of another, the ponds life cycle is interrupted, and the fish go hungry, resulting in skinny fish. Pond Scum And Lake Weeds The Real 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!

Mosquitoes And Skinny Fish

Part 3 in our series and lake and pond interaction

Mosquito questions


Mosquitoes on ponds and lakes may seem to be unrelated to lake weeds and filamentous algae. The truth however, is that mosquitoes become a problem when there is too much vegetation in the pond. Pond scum is the perfect environment to start a healthy mosquito invasion. Pond scum offers the mosquitoes a perfect environment for protecting adult mosquitoes and their larvae from the fish and birds who would normally eat them. Heavy aquatic weed cover also aids in mosquito production, providing cover for mosquitoes against their natural predators like fish and birds.

Poor fishing and skinny fish

Poor fishing quality and poor fish quality are issues that many pond owners experience. They often go hand in hand. Weeds may provide enticing cover for game fish, but if there is too much aquatic vegetation, even getting your lure into the water can become a problem. Low dissolved oxygen, and lack of food can cause fish to (pardon the pun) flounder. The prescience of excessive lake vegetation and mats of pond scum can make fishing a less than pleasurable experience. If the water has too little of one type of algae, and too much of another, the ponds life cycle is interrupted, and the fish go hungry, resulting in skinny fish. There is a connection between all of these elements. Learn what that connection is in: Pond Scum And Lake Weeds The Real Problem

Pond Scum Lake Weeds Mosquitoes And Skinny Fish

Part 1 in our series on pond and lake interaction

The common thread in common lake problems


Controlling pond scum, lake weeds and mosquitoes and raising healthy fish may seem complex and difficult. There is no miracle cure, there is no magic bullet. There are no products on the market which will get rid of your pond scum or lake weed problems, prevent them from returning, and leave you with a healthy pond or lake in the process. Even such biological controls as grass carp have problems that will leave you with even bigger problems than the ones you started with. If all of this makes the situation seem a little bit hopeless, don't lose heart, it is not. Some things are not as simple as they seem. Most people would see pond scum, lake weeds, mosquitoes, and skinny fish as unrelated problems. The fact is, that they are all entwined, and at the root of these problems, is one problem with a seemingly strange, but simple solution!

Lake management looking at the big picture

We took a long look at the questions we receive, and realize that most of them have to do with specific issues, and that they show a common misunderstanding about pond and lake management. They seem to show that many pond owners don't understand how all the parts of a pond or lake interact. Our most common questions revolve around the issue of pond scum, and lake weeds. This is followed by questions which revolve around mosquito control, and poor fishing conditions, and what has been termed “skinny fish”. These issues are commonly addressed as individual issues, when in reality, they all have the same root cause. What we would like to do is show the big picture of how a lake with one thing wrong, probably has several problems, and one main problem which all the others revolve around. See: Pond Scum And Lake Weeds