Pond Algae: This is How to Get Rid of Algae in the Pond

When you see red or green algae forming in your pond, you should not just step in to visually regain your pond. But fighting algae is often not easy. What helps best? Are there any good home remedies? Can you fight algae without chemicals? Here we will tell you how to get rid of algae in the pond.

We will explain you if milk, zinc, soda or even fish and snails are the best help. We clarify the most common myths and explain what really helps.

The Essential Stuff

  • Overgrowth of algae has several causes. These include solar radiation, heat and a nutrient overload. Especially phosphate.
  • Home remedies are not a reliable algaecides. Use plants, animals or chemical algae killers.
  • To counteract algae, you can also reduce the sun’s rays or provide movement in the water.

What is Algae?

Algae, also called seaweed or seaweed, are mostly aquatic plants. They often have no roots, leaves or stems. However, the cells form a plant body with “organs” that can replace or imitate leaves, roots and stems. Algae do not multiply by seeds, as do most land plants. Rather, it is often unicellular organisms that multiply by cell division. They form the basis of the food chain and produce much of the earth’s oxygen.

algae grow on water surface
Algae grow on the water surface and below, in salt and also in fresh water.

There are different types of algae. Often they are divided into their approach to growth. There are single-celled algae, multi-celled algae, which then often look like threads. Some cells also build entire colonies. When algae get bigger, they use a more complicated blueprint. Then they are called Tang.

In fact, algae can also survive on land. Often they are falsely referred to as moss. For example, they grow on tree trunks and endure dehydration. They can also grow on damp cave walls or on muddy floors. Some algae also enter into a symbiosis with mushrooms and become lichens.

Backgrounds: What you should know about algae in the pond

What are the causes of algae in the pond?

Algae are always in your pond. But normally the balance in the pond, which is a small ecosystem of its own. However, should something change, the balance no longer holds.

One cause is, for example, the nutrient concentration in the pond. Normally, for example, the phosphate content is about 0.035 milligrams per liter. Then all plants and animals live peacefully next to each other in the pond. But what happens if something changes? And where does the change come from? We have summarized these questions for you here.

When do algae grow in the pond?

Algae carry out photosynthesis and therefore require sunlight in particular. In addition, they can only metabolize their metabolism if it is warm enough. In addition to sunlight, algae, like all plants, also need phosphorus.

Phosphorus is used as a fertilizer because all plants need phosphorus for growth. Algae, on the other hand, because they have a very simple cell structure, can multiply very quickly and absorb and utilize the phosphorus quickly.

For these reasons, above all

  • sunlight
  • warmth
  • phosphorus

for increased algae growth. If one of these parameters changes, algae can respond quickly.

This happens, for example, in the spring, when the sun shines longer again.

While other plants need a little longer, algae can start cell division immediately and spread out undisturbed.

Even after a sudden heat, the algae start to sprout. Likewise, one can observe an increased growth of algae, when the phosphate level rises. This often happens when fertilizing near the pond or adding something to the pond.

Why are some algae red and some green?

Green is the most common color of the plants. This is because you can see the chloroplasts through the leaves. The chloroplasts are the power plants of the plant. They convert sunlight into usable energy for the plant.

Did you know that there are estimated to be over 500,000 species of algae?
So far, people only use about 500 species. Because many algae are poisonous for humans and animals. In addition, algae absorb many heavy metals that are contained in the water.

If you see red or brown algae, it’s because chlorophyll contains other color pigments as well. These overlay the green of the alga and give it another characteristic color. The combination of these pigments can produce a wide range of colors. Algae are also available in scarlet or bright blue.

red algae seaweed

Can you remove algae from stone?

Algae grow in pretty much all places. Not only can they grow in the water, they can even bond with mushrooms and grow on stones on land. Then they are called lichens.

Even in the water, plants attach to different places. Partly they simply float on the surface, but sometimes also on the bottom of the water, on other plants or on stones.

Often the complete stones overgrow then and are covered with a slippery, green film of algae. It is very time-consuming to liberate the stones from the algae. It’s best not to do this by hand, but let the animals take over for you. How exactly this works, we explain in the following section.

Can you remove algae from the pond?

When algae multiply explosively, they often overgrow the entire pond. For the balance of the pond, it is important to curb the growth of algae. If your pond is attacked by algae that swim on the surface, you can also fish it off.

Use a net and remove the algae. Make sure you also fish algae that grow close to plants. Repeat this process every few days as the plants can replicate quickly.

This tactic is effective, but it is very time consuming. Nor does it fight the cause, only the effect. To counteract algae from the ground up, you should take the following steps, which we will explain to you in the next section.

What to do against algae in the pond: What are effective ways to get rid of the nasty green?

Can you remove algae from the pond with home remedies?

The Internet offers a wealth of home remedies for algae. Whether or not they actually work is explained here.

Often, milk is treated as a true wonder drug. The theoretical consideration behind this is that the lactic acid that forms in the water should kill the algae.

Practically, however, the effect is unproven. In addition, milk also contains milk sugar, fats and proteins, which serve as a source of nutrients. In addition, large amounts of milk can severely damage balance and water quality.

milk on algae

Another idea is the addition of soda. However, this is also not a good idea. Because to actually create an effect, you need a large amount of soda. This will disturb the delicate balance in the pond and probably kill many creatures and plants.

Also vitamin C is traded as algae killers in the pond. In fact, algae disappear after adding vitamin C, but this is more likely to fight algae in the pool. In addition, the decline in algae is only a short-term reaction to the vitamin, but will not solve the problem in the long term.

None of the listed home remedies can remove algae from the pond!

The pond is a living system on which many animals and plants depend, please pay attention to what you supply to the pond. And there are plenty of alternatives that we’ll explain in more detail in the following paragraphs.

Which plants can destroy algae in the pond?

Other plants in the pond are a direct competitor to algae. If you take care of them, algae have little chance of getting the upper hand.

Good for it are different plant species. Here is a list of potential options.

  • chickweed
  • crab claws
  • frogbit
  • duckweed

These aquatic plants have the common feature that they reach the surface of the water or immediately float on it. As many algae grow very close to the water surface, the aquatic plants limit the possible habitat of the algae. In addition, they leave less nutrients for the algae.

Damit der Plan aufgeht, solltest du darauf achten, dass etwa ein Drittel deines Teiches mit Wasseroberfläche bedeckenden Pflanzen bewachsen ist. Ob sie dabei wie die Wasserlinse darauf schwimmen oder wie das Hornkraut darunter treiben, macht keinen Unterschied.

frog and algae in the pond

Are there any animals that eat algae in the pond?

Instead of plants, you can also use animals as algae fighters. Animals destroy algae by eating them.

Many fish feed on algae. This has the advantage that you do not have to feed the fish yourself. In addition, it often looks nice when a few fish frolicking in the pond. Be careful, though, that it will not be too many fish. Because their excretions can favor algae growth again. Here we have summarized what fish is suitable for your pond.

Rudd20 -30 centimetersSmall pond
Silver carbup to 130centimetersLarge pond

Otherwise, snails are also very good. They are a kind of “lawnmower for the pond”. In particular, the marsh cap slug is popular, as it not only frees the bottom of the pond from algae, but also algae that float on the water surface can eat. The Spitzschlammschnecke, Posthornschnecke or small Schlammschnecke only eat algae on the pond bottom.

Did you know that algae are true miracle plants?
Because they are pumped full of minerals and valuable vitamins. These help to stabilize the climate of the earth and serve as a food source.

But mussels and crustaceans are hungry algae killers. The pond mussel filters around 1,000 liters of water per day and also eats suspended algae. Freshwater shrimps like to feed on algae on the water surface especially as young animals. Also rotifers, which are zooplankton and are microorganisms, rather algae. They eat many times their body weight of algae and multiply explosively when many algae occur.

With all the benefits of algae-eating animals, keep in mind that they also need food when there are no algae left.

In addition, these animals can often multiply quickly. Best discuss this with an expert in the gardening market.

Which chemical algae killers are there?

In the trade you will find a wide range of chemical algae killers. But be forewarned, because these are an intervention in the system of the pond and burden this often long after their use.

Although algae killers are always advertised as being safe for other plants and especially fish, you should be aware that algae killers only fight the symptoms. The reason why you have so many algae in the pond remains.

Algae killers can be purchased both on the Internet and in hardware stores or garden centers. These are not cheap though. Expect a price of about 20 $ to even 170 $ per kilogram. However, you need different amounts of each product.

Trivia: What else you should know about algae in the pond

Why do the algae in the pond come after the winter?

In winter there are much less hours of daylight compared to the summer in Central Europe. All plants suffer from this because they need sunlight to be able to convert energy. Therefore, the plants stop their growth and wait for a while.


When spring dawns, the realm of plants starts right. The increased sunlight and especially the warmer temperatures are used immediately. However, algae, due to their simple construction, can make use of the changed situations immediately and much faster. In addition, they do not need as much heat as their neighboring plants.

The new habitat is immediately absorbed by the algae. Often this happens so fast that other plants have no chance and the algae can spread unhindered.

Why are algae in the pond despite filters?

Filters do not help with all types of algae. They only help with suspended algae. Thread algae are rooted directly on the ground and can not be absorbed by a filter. So the fear that the filter would be too weak can not be confirmed.

Sometimes, however, the filters just are not strong enough anymore. However, since the filter contains important bacteria, you should express the sponges in the pond water so that the bacteria remain there.

How can you prevent algae in the pond?

A movement of water in the pond is unpleasant for algae. A small fountain in the pond not only looks pretty, but also makes it easier for the simple plants to capture the pond.


Since algae necessarily need light, it may be useful to shade the pond. That should severely limit algae growth. For this you can plant a tree next to the pond or, if your pond is severely affected, put a shade over the pond for the summer.

What can you do to never have algae in the pond again?

Algae are disturbing, do not necessarily look good and negatively affect other aquatic plants. However, algae will appear again and again in your pond, should the conditions be right.

Therefore, try to counteract algae as much as possible and to create conditions that the algae do not like. Animals, plants, shadows, movement in the water and a balanced nutrient supply can prevent the growth of algae.


Algae are an unpleasant side effect that many garden owners unfortunately know enough. There is no lasting remedy for algae, but you can specifically target algae with plants and algae-eating animals. Even chemical algae killers can help.

Nonetheless, keep in mind why the algae in your pond suddenly gained the upper hand. Because the gardener saying “If the plants go bad, the algae are good” is not true. Presumably there is simply a nutrient over supply that only the algae know how to use. If you counter this, you can keep the algae at bay.