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 into how to treat the green menace, let's discuss the different species of algae and where you are likely to find them in an aquatic ecosystem.
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 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 KnockDown Defense, 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 EasyKlear Defense, 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 Rake, setting up an aeration system and adding natural bacteria, such as the types found in ClearPAC Plus Pond Care Package.