How to remove algae in a pond?

How to remove algae from a pond? This is one of the most complicated concerns to manage when starting a garden pond.

Have you just come across this article and are wondering how to easily remove algae in a pond? We'll explaine everything here !

Algae is a problem for all water surfaces , ponds, lakes, rivers and other bodies of water. But the term "algae" is often used to refer to different plants. It will be necessary to dissociate the aquatic plants from the algae which are "gaseous" structures. However, not all aquatic plants are algae. And not all aquatic plants are the same: there are plants that are beneficial and others that are undesirable and harmful to your pond.

In this article we will talk about this topic and how to get rid of existing algae and how to prevent its appearance.

What are algae?

Even specialists do not agree on how to call or classify algae. Defining what an algae is is very difficult, but generally speaking, algae are simple organisms that can even consist of one or more cells grouped together in colonies and living in an aquatic environment. There are four main types of algae: blue algae, string algae, unicellular algae and slime algae.

Blue-green algae are unicellular (planktonic) and microscopic plants that can grow in any body of water. They can bloom in different colors: bright green, apple color or blood red.

They are the base of the food chain, and a healthy pond should contain this type of algae as a food source for other living organisms. But overgrowth can turn your pond into a swamp. Blue-green algae have recently been reclassified from the algae group to the Monera group, which includes bacteria, because blue-green algae are closer to bacteria than other types of algae.

Blue-green algae come in different colors, for example red, brown or yellow. Blue-green algae are nitrogen-fixing organisms and need nitrogen to live, as well as carbon dioxide, which are very common substances in most ponds. When blooming, blue-green algae form dense masses on the surface of the pond water and can cover the entire surface.

String algae are mossy-like plants that typically grow in water or cover the surface of rocks in water as greenish "mossy" formations. These colonies of united cells have a slimy, mossy texture while the algae attached to the surface have no roots, but have a dense structure. String algae thrive in water with a high calcium and phosphorus content. Generally, this type of algae comes to life after adding lime to ponds to increase fish production. They usually appear in warm areas of the pool and can grow to cover the entire surface of the water.

Slime algae is usually slimy, hard or spiky in texture, often causing the most damage when it becomes a problem for fish.

Problems caused by algae

In general, the most common complaint about algae is that it detracts from the aesthetics of the pond. A green pond covered in algae is not pleasing to the eye. When algae cover the surface of the pond, it is not a pleasant sight.

Algae pose a problem for the health of your pond when they are too numerous and when they bloom. During photosynthesis, plants absorb sunlight and carbon dioxide and release oxygen. Photosynthesis is a beneficial process for every pond. Oxygen is necessary for the decomposition of organic matter and for the life of fish and other species living in the basin. However, photosynthesis only takes place in sunlight. As soon as the sun goes down, plants stop producing oxygen and start consuming it.

Therefore, the more aquatic plants and algae there are in your pond, the more oxygen they produce during the day and the more they absorb during the night. The concentration of oxygen in the water decreases considerably during the night. The lowest concentration of oxygen in the water is just before sunrise.

Excessive algae growth also limits the penetration of sunlight into your pond water, which can cause significant thermal stratification of the water. Water that does not receive sunlight and heat cools and becomes denser. The concentration of oxygen in the water decreases because it is not in contact with the air. It can also reduce the mixing of waters in the fall and spring.

Algae Control Measures

There are many known ways to control and prevent algae growth. These include herbicides, bio-additives made from beneficial bacteria, chemicals, ultraviolet sterilizers, and herbal supplements like barley straw. Each treatment acts on the algae in its own way and under different conditions, with different effectiveness. Some products are only effective for one algae bloom cycle, others may be effective for a longer period. Take a look at the cleaning methods below, along with their pros and cons.

Coloring substances

Using the water staining method is old technology, but it continues to be used and pays off. Special powder or liquid paints, blue or black, are used which darken the water and reduce the penetration of sunlight necessary for the growth of algae. Enzymes and pond dye are available for this purpose. Another benefit of coloring the water blue or black is that it prevents predatory birds from catching fish in the pond, as it would then be more difficult for them to do so due to diminished vision from the color.

But it is not always easy to buy special paints. Also, this method of treatment does not work well in ponds designed for irrigation or connected to other bodies of water because the paints are washed away as the water moves. Nor is it always acceptable to tint the water in decorative ponds.

Bacteria and enzymes

The application of beneficial bacteria is not a chemical method. It works primarily with living organisms that consume nutrients that would otherwise be available to plants. It is usually a concentrated mixture of bacteria and natural enzymes that quickly break down sludge, improve water quality, reduce suspended solids and eliminate odors. 

The bacteria effectively eliminate lower plants (algae) without damaging higher aquatic plants. Indeed, the bacteria block the surface of the lower algae and it is through the cell membranes of their stems that the metabolism of the plants located at the lower level of the surface takes place.