Large Ponds

Every summer the ponds around us turn green.  Some don’t of course but many do and the culprit is some type of pond algae.  Algae is on of the oldest forms of life on earth and it thrives when certain conditions are met and farm ponds just happen to have many of these in abundance.

In this article we want to address some of the reasons why a pond may develop an algae problem and more importantly what you can do to clear things up.  Larger ponds and small lakes are not always the easiest or most inexpensive to treat but clearing can be achieved by taking proper action.

What Causes Algae?

Algae, like any plant will need certain things to survive and thrive. Namely it will require ample sunlight and adequate levels of nutrients to support it. These nutrients may come in the form of phosphates, nitrates, nitrates, or other organic elements. They enter the water through run off or may build up as organic things such as leaves or grass clippings fall into the pond and begin to decay. In simple terms I’ve always compared this to compost in a garden. You add decaying organic material in there to help your veggies grow and the same things will help algae grow well too.

Larger ponds and small lakes are almost always impacted by environmental factors like this. Other things, like heavy fish populations that might affect a smaller pond, will normally not support abundant algae growth in a larger one.

Light exposure as well will support algae and this is why shallower waters tend to have algae growing in them first (or if they are around the edges of a pond run off could create this too). Some single cell algae will in fact rise and fall in the pond during it’s daily cycle. In the morning it will come to the surface to pick up energy from the sun through photosynthesis. At dusk it will sink once again to spend the night at the bottom of the pond.

As the weather warms in spring and summer, and sunlight becomes more plentiful, algae will tend to grow more prolifically. In fall and winter it’s often not as much of a problem, however in ponds with high nutrient loading, you may see algae growing under the ice in the early spring.

Algae Control 101

Knowing the things that support algae is really the first step in figuring out the best way to control it. After that we can narrow down our options into a sensible plan of attack. In shallow waters, something like pond dye or a tinting additive will help limit the algae’s exposure to light. These come in several shades such as blue, black, or a combination of the two. They are relatively affordable and can last a month or more in many ponds. The turnover rate or amount of rainfall may affect this time somewhat.

Other common options usually include some form of chemical treatment such as with an algaecide, biological treatments, or some type of manual removal, although the latter isn’t very easy to do in big bodies of water.

Algaecides Kill Algae But…

Over the years it’s been a traditional thing to try and kill the algae growth outright with something like an algaecide. Most of these contain some form of copper in them, and this is because the substance is toxic to algae. Algaecides can and do work well in at least clearing the surface of the algae problem. One drawback to using them however is they support the build up of organic material at the bottom of a pond and this, unfortunately, can support more algae growth.

For an algaecide to be used correctly, it’s best to apply them as a preventative measure rather than a treatment. If algae can be controlled early on before it takes over the pond, the build up of dead matter at the bottom is reduced and many times less chemical can be used in the process.

If algae can be brought under control, the pond may stay clear for some time, or applying the algaecide may become a matter of routine maintenance.

The Beneficial Bacteria Connection

One of the most useful things found in a natural farm pond is the existence of beneficial bacteria. These are good bugs and microbes that nature has designed to help keep the pond cleaner. They help clean up muck and organic material at the bottom of the pond and can even consume some of the nutrients from run off and organic decay.

Because they prefer some of the same thing that algae does to thrive, they can quite often out-compete algae for these resources. When they do, algae of all types (other than Chara) may regress and disappear. This makes them a valuable ally to farm pond algae control and supporting their health and vitality is a good step to take.

It’s important to note that many chemicals, including copper algaecides, will hinder or knock down this bacteria. Therefore if chemicals are applied, it’s often suggested to supplement or add fresh bacteria into the pond to help replenish them. There are many brands and blends of bacteria on the market but they are all intended to work in a similar way in a lake. Some are temperature sensitive so the blend may be changed depending on the season and conditions.

Pond aeration helps to add oxygen into pond water and this is a very useful step to support beneficial bacteria since this is primarily aerobic in nature. Higher oxygen levels will help them thrive and increased circulation will provide increased mobility throughout a large pond.

Algaecides and bacteria do not work together well in most cases and cannot be combined, therefore it’s important to decide or plan out your intended algae control method before you start treatment of any kind. Pound for pound, biological control may cost more in the beginning compared to a chemical application, however as we’ve noted earlier, if chemicals are misapplied, they can take a pond in a poor direction and create more problems later on.

What About Barley Straw?

Finally we would be remiss to not talk a bit about barley straw. Many old farmers swear by it for algae control and there is some merit in their words. Historically barley straw has been used in Europe for some time and in recent years it’s made it’s way to the U.S. It works well in some ponds and in others it seems to provide no great help at all.

Recent research by several universities including Ohio State have shown that barley straw is best when it’s thoroughly dried and bundled in a bale or mesh material. In tests it appears to work best when it’s applied before algae has shown up in a pond and may retard new growth. It seems less effective on algae that is already present.

A one acre pond would likely use about 2 to 3 standard bales and these can last up to 3 or 4 months before they would need to be replaced.

Barley straw releases a substance as it decays and some experts believe this breaks down into a very light form of peroxide which damages new algae cells. Further research however is necessary to determine why and how the straw works at all.

Algae Can Be Controlled

The most important thing to remember is that even though algae may show up in any body of water, no matter how large. There are ways to either keep it in check or rid the pond of it entirely. Some of the steps an owner might take will depend upon budget constraints, if the pond has an active fish population and any environmental concerns. However with the right knowledge, and a basic understanding of why algae grows at all, one can make progress towards a cleaner farm pond.