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Does the type of algae and where it’s growing determine what chemical is needed? | Ponds & Lakes Q&A


Q: Does the type of algae and where it’s growing determine what chemical is needed?

Q: Does the type of algae and where it’s growing determine what chemical is needed?

Pete – Addison, AL

A: When battling algae, you have the upper hand if you understand the enemy. What type of algae is it? How does it behave? What are its strengths and weaknesses? Before we get in to how to treat the green menace, let’s discuss the different varieties and where they live in an aquatic ecosystem.

Algae Explained

In a large pond or lake planktonic algae, filamentous algae and chara, are the most common types of algae you’ll come across.

  • Planktonic algae, the source of algae blooms, are floating, microscopic plants that color pond water shades of green, blue-green, brown or variations in between. In controlled amounts, this type of algae can actually be beneficial. It can shade the pond’s bottom, preventing subsurface nuisance plants from growing.
  • Filamentous algae are single-celled plants that form long, visible chain, threads or filaments. These threads, which start growing along the bottom of the lake in shallow water or on rocks or other aquatic plants, intertwine and form mats that resemble wet wool. When these mats rise to the surface, they’re commonly referred to as pond scum.
  • Chara is a gray-green branched multicellular algae that has 6 to 16 leaf-like branchlets that grow in spirals around the stem. Though bottom-growing chara superficially resembles terrestrial plants, it lacks flowers, true leaves and roots. It has a skunky, musty, garlicky-type smell and has a crunchy- or grit-type texture, thanks to calcium carbonate deposits on its surface.

In general, algae will grow just about anywhere sun penetrates the pond. Surprisingly, algae has some benefits: The tiny plants feed fish and make great homes for micro- and macro-invertebrates like bugs and worms. But algae has its definite drawbacks. Besides being unsightly and odorous, uncontrolled blooms can cause oxygen depletions, affect fish health and, in extreme circumstances, cause fish to die.

Vanquishing the Menace

The key to successfully treating algae – whether planktonic, filamentous or chara – is to make the most contact between it and the algaecide. Rather than dumping the chemical into one place in the pond, which will only kill algae in that small area, it needs to be evenly dispersed.

Floating mats of filamentous algae and suspended planktonic algae are best treated with liquid mixtures, like Algae Defense® and Clipper™, that are sprayed directly over the area with a pond sprayer. To treat extra thick mats, stick the top of the sprayer into the mat itself to get the chemical to the deeper portion of the problem.

For bottom-growing algae, use granular algaecide, like Cutrine®-Plus Granular and Hydrothol, and distribute it with a granular spreader. It’s the preferred choice because the granules will sink over the algae bed and make maximum contact with it.

Follow up by raking out any decaying or dead debris with the Pond & Beach Rake, setting up an aeration system and adding natural bacteria, such as the types found in ClearPAC® PLUS Pond Care Package.

Pond Talk: How much time do you spend battling algae in your pond or lake?

Spray Directly Onto Algae Blooms - Pond Logic® Algae Defense®

2 Responses

  1. This year, I have been battling Filamentous algae for the first time. I also have, for the first time, plant growth at the bottom of my pond. I have been raking and cutting the plant growth regularly which has been keeping down the bloom but do you have a chemical that can kill the plant growth? If so, when is the best time to treat the pond? Ed Wacks

    • Hi Ed – As long as you do not have koi or trout in the pond I would recommend Algae Defense & Treatment Booster PLUS for the algae growth. For the other weed growth you would need to identify what type of weed it is in order to select the best treatment. You can try to match it up with our weed control guide and then click on the picture for treatment options, send us a sample in a dry papertowel or e-mail us a picture and we can assist with identification. You can treat the weed and algae growth as long as water temperatures are above 60 degrees and the weeds and algae are actively growing.

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