DIY: Removing algae from pond


Whether you accept it or not, algae are a part of any water body there is. If you plan to put up a pond garden, for example, be prepared to carry some duties like sustaining the pond’s cleanliness. Since it is a water system, algae will quickly flourish, especially on the surface, if not cleaned accurately. 

There are, however, a few DIY ways to deal with these plant-like organisms. Let’s begin.

Understanding algae:

Algae are simple plants that, via photosynthesis, combine carbon dioxide and water to form sugars for growth and energy. Algae produce oxygen, a vital by-product, but when sunlight is not accessible at night, they quickly respire. This respiration uses the stored oxygen and sugar to form carbon dioxide, which depletes the pond’s oxygen. There are basically two kinds of pond algae:

  1. String Algae: This filamentous species, which evolves in long strands, adheres to waterfalls and rocks. They ultimately tangle together, forming dense, ugly mats that can double their weight within a day. (scary, right?)
  2. Green Water: These single-celled organisms—which stay suspended in water—are so tiny, they pass through even the smallest filter. If conditions are perfect, meaning there’s plenty of sunlight and nutrients, as many as five million algae cells per milliliter of pond water can be present ( I am not kidding).

Let’s see how to eliminate it now.

In a natural environment, fish produce nutrients absorbed by plants, leaving nothing for the algae. However, many private garden ponds do not hold enough plants to check all the fish’s nutrients. This causes a buildup and provides an ideal environment for fast algae growth.

Whether you’re just starting and want to withdraw algae problems or have an existing issue to control, you’ll first want to double the number of oxygenating plants on the exterior of the pond. This is perhaps the most straightforward, long-term solution to keeping water clear and clean.

Floating plants, such as lotus and lilies, reduce direct sunlight and provide shade in the pond to regulate algae’s growth. Add submerged plants that deliver oxygen to the water, such as hornwort, anacharis, and my favorite parrot’s feather. As a guide, one bunch of four strands of an oxygenating plant can be attached to every one square foot of water surface and submerged by planting in a soil container or tying to a rock.

All aquatic plants also consume nutrients and starve the bad algae. After initial plant installation, green water may occur but will last only a couple of days. You can plant established marginal plants around the pond’s periphery or in small sections of the pond. These are also useful in providing shade and absorbing nutrients.

One favorite way to add plant life into the pond system without putting plants into the central pond is by constructing a plant filter. A plant filter is a small filtration pond or simple channel through which water from the pond is fed relatively slowly. Fast-growing plants (suitable nutrient removers) are grown within this little pond in planting pots or are free-floating, such as water hyacinth or water lettuce. Ideally, you should line the plant filter with about 1.5″ of pea gravel, which is the best substrate to root the plants.

The pea gravel catches debris and acts as a bed for beneficial bacteria. As these plants grow, they absorb nutrients from the water and “out-compete” algae to control its growth. Generally, the plant filter needs to be stocked with plants equaling about one-fourth of the main pond’s surface area.

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