How to prevent your pond from greening?

Green water in a pond is caused by the proliferation of single-celled algae or cyanobacteria (the scientific term for blue-green algae), which not only spoil the appearance of the pond but also disrupt its ecosystem.

The water turns green and gives off an unpleasant odor, and a clogging phenomenon occurs. This is dangerous because invasive algae prevent light and air from penetrating deep into the pond and hinder the growth and development of other aquatic plants. The lack of sunlight and oxygen can lead to the death of the fish living in the pond. However, if the water is moving and well oxygenated, it can be green without being toxic to the living creatures in your pond.

Main causes of green water in ponds

The growth of vegetation in standing water is a natural process that helps restore the ecosystem of water bodies after winter. Only take action if the spring bloom lasts more than 10–14 days. In summer, however, you should start combating clogging as soon as you notice the first signs of this phenomenon. There are several reasons for this process:

• Stagnant water in the pond with little aeration;
• Too much organic matter (dead leaves, pollen, etc.);
• Too much plant fertilizer and fish food;
• Nitrogen- and nitrate-rich lawn nearby;
• Degradation of the liner;
• Sludge caused by fish excrement.

Preventing pond pollution

Proper pond cleaning helps prevent the pond from becoming uninhabitable over time and turning into a swamp. A complete pond cleaning involves draining all the water, moving the fish to tanks, and mechanically cleaning the bottom and walls of the pond of sludge and algae.

It is advisable to drain your pond at least partially and use a filtration system suited to your body of water. You can also use a pond vacuum to clean debris from the pond. To avoid having to go through this procedure too often, follow our tips:

• Throughout the season, clear the water surface of excess algae, dead leaves, and other debris;
• In spring, give your fish high-protein food (this helps them recover more quickly from winter, even if they did not spend the winter in the pond);
• Perform a thorough inspection of your fish every spring;
• Isolate sick fish from healthy fish;
• Inspect the bottom of the pond before the start of the season to check that it is not damaged (even if you have not drained the pond or overwintered the fish inside);
• If you cannot regularly clean the pond of dead leaves, cover the surface of the pond with a fine-mesh net in autumn.

How to clean a pond of green algae?

There are several ways to clean a fish pond:

• Manual pond cleaning
• Cleaning the filtration system;
• Filter installation;
• Cleaning with a skimmer;
• Cleaning with a pond vacuum;
• Cleaning with a flocculant (such as Oclear);
• Planting special filtering plants;
• Water treatment with bio-additives;
• Use of ultraviolet lamps;
• Introducing certain species of fish into the pond.

How to clean a pond manually?

• Remove excess vegetation (including invasive cultivated plants) from the edges and weeds.
• Remove dead leaves, twigs, and other organic debris from the surface of the pond using a net.
• Remove duckweed and invasive algae with a fan rake.

Use of pumps and filters

Installing a filter is one of the most popular ways to maintain a balanced pond ecosystem. This device not only removes harmful impurities from the water but also oxygenates it.

Standard artificial pond filters use a three-stage purification system: mechanical, biological, and ultraviolet. Such a device not only removes mechanical impurities from the water that cause the pond to become saturated but also deprives harmful plants of nutrients. All filters are divided into two main groups:

• Flow-through filters are suitable for use in large ponds with fish;
• Pressure filters are ideal for small ornamental ponds.

Removing debris with a skimmer.

A skimmer is a device that removes debris from the surface of the pond. It is essentially a pumping device that filters the water and sends the remaining debris into a basket. Depending on where they are installed, these devices are divided into three categories:

• Bottom skimmer;
• Shore skimmer;
• Surface skimmer (floating).

The main disadvantage of a skimmer is that it cannot clean the bottom of the pond of accumulated sludge. This is why skimmers are most often used as a complementary tool rather than as the main method of cleaning the pond.

Cleaning the bottom of the pond with a vacuum

The basic principle is practically identical to that of a vacuum cleaner. The device sucks water from the bottom of the pond and filters it, sending the dirt and sludge accumulated in the basin of the pond into a specially designed dirt trap.

Chemical cleaning of the pond

You must be very careful with this cleaning method because the careless use of chemicals can kill the aquatic plants and fish in the pond. This is why experts recommend it only as an exception. You can buy a pond cleaning product in specialty stores.

The safest thing is to use chemicals in spring, before filling the pond with fresh water and adding fish (2 to 3 weeks before the scheduled start of the season). Use only products intended for ponds, following the doses and precautions indicated on their label.

Preventing a pond from turning green using plants

Planting cultivated aquatic plants is a very effective way to combat green water:

Marginal plants (irises, lilies, cattails) prevent weeds from growing;

Aquatic plants (water lilies, water nymphs) absorb nutrients directly from the water and thus prevent the growth of harmful vegetation;

Subaquatic plants (water pepper, eelgrass) take root in the soil of the pond and also prevent the growth of unwanted algae.