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Pond and Lake Algae: Friend or Foe?

This article has been contributed by Lake Restoration

We often think of algae as annoying green scum covering our fish tanks, ponds, and water features. Sometimes we think of those “algal blooms” that happen every summer. We walk by lakes, reservoirs and ponds with noses turned up at the awful smell as valuable oxygen is consumed and other water life forms are asphyxiated or poisoned. We mostly assume that the pond or lake is afflicted and beyond repair. We also dismiss algae as disruptive and unnecessary. But is it?

algae ponds lakes

For those who own or manage small ponds or lakes, the struggle to keep algae in check is an ongoing headache, but it’s a mistake to dismiss algae as inherently evil or that nothing that can be done when it takes over. The secret, rather, is a little knowledge, some handy pond and lake weed control products, and a philosophy of keeping your water body and algae levels nicely balanced.

First lets look at what’s happening. When temperatures change or there is a die-off of underwater plants, an excess of nutrients is released into the water that result in an algae feeding frenzy. Algal concentrations rise in some of these cases to millions of cells of algae per milliliter of water.

The types of algae usually found in water features, ponds, and lakes are either floating, pea soup looking algae — a.k.a. blue-green algae (actually a bacteria known as cyanobacteria) — or the stringy filamentous algae that often looks like a solid mat of green goop that frequently attaches itself to rocks or other plants. These algaes can easily get out of control and grow very quickly. The problem isn’t the living algae, however. The problem is the the short life span of the algae and a high concentration of dead organic matter left behind, either in the water or on the surface. This process consumes large amounts of oxygen and often leads to the asphyxiation of other species.

Would a pond or lake be healthy without algae? Not really. Algae is important to the food chain within any lake or pond. As primary producers they use sunlight to produce food which is then consumed by little animals like water fleas and microscopic organisms. These are, in turn, grazed upon by fish, which are then eaten by bigger fish, etc. A healthy and productive lake produces large fish and good fishing for humans as well as supporting food and habitat for wildlife and waterfowl. In this way most algae are desirable for lakes and ponds.

Overall, algae isn’t good or bad on its own. The important thing is to keep your algae levels well-balanced. Here are a few tips:

First, keep in mind that one of the things that makes a pond so lovely could be the very thing causing the algal issue in the first place — fish. Algal blooms begin with the presence of excess nutrients, and fish are often the very thing providing those in the form of waste and excrement. For stewards with the ability to manage their fish counts, keeping fish numbers low can result in a less work and expense in the long run.

Secondly, it never hurts to add a little competition to the mix. By adding decorative plants you not only increase the competition for nutrients but you also create shade for the water below where sun-loving algae won’t thrive.

Thirdly, any time a body of water has excess nutrients, the chances of an algal bloom occurring increases. These nutrients often come from fertilizers we put on grasses that surround our lakes. Sometimes managing your lake means managing your watershed area, too. The goal of the perfectly green lawn could in fact be contributing to your perfectly green lake. Algae eat the same things as your grass, so use care when treating your lawns and remember that you’re treating your lake as well.

There are many ways to help control algae in a lake or pond directly using safe and natural algaecide treatments to bring back the balance of nutrients, kill and keep algae in check, and reduce phosphorus levels. There are also pond dyes available that not only keep the sun from being a nutrient source for algae but also increase the healthy appearance of your pond and lake water.

Algae often gets a bad reputation, and although it can get out of control, a little algae is good. It is after all the food base for all marine and freshwater life. It feeds the slightly larger organisms, that feed the bugs, that feed the birds and the fish that sometimes feed us. As in many areas in life and nature, the goal is moderation, and that requires keeping a careful balance of algae in our bodies of water.


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