Last updated: August 7, 2021

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Welcome to our big algaecide test 2021. Here we present all the algae killers we have tested in detail. We have compiled detailed background information and added a summary of customer reviews on the internet. We would like to make your purchase decision easier and help you find the best algae killer for you.

You will also find answers to frequently asked questions in our guide. If available, we also offer interesting test videos. Furthermore, you will also find some important information on this page that you should definitely pay attention to if you want to buy an algae killer.




The most important facts

  • Algaecides, also known as algaecides, are a type of biocide and act against algae. They kill the algae and at the same time fight the growth of new algae.
  • Actually, algaecide can be used where there is water or where it is damp. E.g. in aquariums, in ponds, in swimming pools, in water reservoirs and fountains and in water tanks.
  • The application of algae killer for beginners is quite simple. There are usually instructions on the packages and then you know how much and how often algaecide should be used to keep the water free of algae.

The best algaecide: Our picks

Guide: Questions you should ask yourself before buying an algae killer

What exactly is an algae killer?

The algae killer is a chemical agent against algae that not only removes the existing algae but also prevents the growth of new algae. Because algaecide is also an insecticide, it is often known as algicide.

What is algaecide used for? What are the applications?

It is certainly not nice when your garden pond or swimming pool has turned green or even black and is swampy.

This is caused by the proliferation of algae and you would need to clean your water tanks thoroughly, for which you need algaecides.

Theoretically, algaecides can be used as soon as there is water. Algaecides are most commonly used in aquariums, ponds and pools.

They are also very often used in construction in facade coatings and insulation materials, in cooling towers or in antifouling coatings on ship hulls.

Furthermore, they are also important for terraces, pavements and facades, because algae grow wherever there is moisture, i.e. not only in water.

What active ingredients are there in algaecides?

To remove algae as well as to curb their growth, the following active substances, among others, are to be used:

  • Monolinuron
  • Humic acid
  • Pelargonic acid
  • Methylmethanamine

Depending on the area of application, you should choose the appropriate product, e.g. products with pelargonic acid are usually preferable for garden ponds.

How quickly does the algaecide work?

With algaecides the algae are destroyed quickly, usually after several days they are gone. It is important to bear in mind that you should leave the anti-algae agent in the water for at least 24 hours.

Why does algae form in my pond or pool in the first place?

Most algae in aquariums belong to the lower water plants that are undesirable.

The formation of algae cannot be completely prevented, but increased algae formation is always an indication of an imbalance or non-optimal conditions, points above all such as less than ideal sunlight or artificial lighting, too abundant feeding, too few water changes as well as overstocking should be taken into account.

While algae are usually perceived as atmospheric at the seaside, the opposite is usually true in one's own garden pond or even pool. (Image source: pexels.com / Saad Bouzaid)

How much do algae killers cost?

We have compiled the prices of the anti-algae agents on amazon.de according to the shapes of the products to give you a rough idea.

In a large price study, we examined a total of 240 products from the algae killer category to give you an overview. You can view the results here in our graph. Find out in our guide whether a product in the higher or lower price range is suitable for you. (Source: own representation)

Basically, algae killers that remove algae are more expensive than algae preventers that prevent them.

Form Price
Liquid 4,20€/litre~24,00€/litre
Powder 7,00€/litre~17,03€/litre

How often or how much algaecide should I use?

Specific instructions for use can be found on the package of the respective product, and you should read them carefully before use.

The intensity of the algae infestation is also decisive for the frequency and volume of the algaecide to be used.

Generally speaking, one litre of algaecide should be sufficient for thirty to forty litres of water to be treated and one weekly application.


Are there alternatives to algaecide?

Instead of buying the algaecides, they can also be replaced by some household remedies.

It is more environmentally friendly and cheaper: you can use e.g. grapefruit seed extract, tooth-cleaning Corega Tabs or some household cleaners, but don't forget that here again you should be careful with the toxic effect of the household remedies.

One more little trick: milk is also quite a good and easily accessible substitute for the algaecide! In the following video, it is used to remove algae:

For all alternative products, you should always rinse them with running water afterwards.

Decision: What types of algaecides are there and which is the right one for you?

Depending on the application purposes, a different algaecide is always suitable.

To find a suitable product, you should first make clear where you will use the algaecide, e.g. whether in swimming pools, in garden ponds or on terraces.

It is also important to know whether you want to kill the algae that have already formed or prevent the algae from forming.

Some of the most frequently considered purchase criteria are analysed in more detail in the following section.

What are the advantages and disadvantages of the algae killer?

Of course, the algae killer has advantages, but at the same time it also has undesirable side effects and other problems.

Advantages
  • Killing algae quickly
  • Keeping water as well as water tanks clean
  • Fast impact
  • Mostly environmentally friendly
Disadvantages
  • Chemical products
  • Poisoning other plants
  • Carrying heavy damage
  • Short duration of action and hence frequent use

Buying criteria: You can use these factors to compare and evaluate algae killers

In the following we would like to show you which factors you can use to compare and evaluate algae killers. This will make it easier for you to decide whether a particular algae killer is suitable for you or not.

In summary, these are:

  • Type
  • Form
  • Ingredients
  • Frequency of use
  • Efficacy and duration

Type

There are various algae killers for different application purposes, among them are, for example, pond cleaners, aquarium cleaners, pool cleaners, green deposit removers as well as algaecides for terraces and facades.

And according to the mode of action, a distinction must be made between whether the algaecide has a preventive effect or removes the existing algae again.

In the case of the first type, you should add such algaecides to the water directly when filling it to prevent the algae from appearing.

The types of algae should of course also be taken into account, there are for example algae, green algae, falden algae and floating algae. Depending on your needs, you could choose the product you need.

Form

Most algaecides are in liquid or powder form, and there are also algaecides in tablet form.

Ingredients

In addition to the aforementioned ingredients, points such as these also play a role in the selection: Is the product foam-free, chlorine-free or biodegradable?

Here, a rule of thumb applies: If there are positive answers to these questions, then this product is to be preferred.

It is much more recommendable if the products are compatible with plants and animals.

It is particularly worth mentioning that products containing chlorine can only be used in swimming pools, but not in the garden, as they are highly oxidising and therefore toxic.

By the point "biodegradable" it is meant that the anti-algae agents must be environmentally friendly and not harmful to health and thus not contaminate food.

But that is why they have to be used again and again, otherwise they will lose their effect.

Frequency of use

In the product descriptions, you will find the frequency of use and dosage instructions for each product. This information mainly determines the costs as well as the time required, which can also influence your decision.

Efficacy and duration of effect

The stronger the efficacy and the longer the duration of action, the better the product is in terms of breaking down or preventing algae, but at the same time it can be more difficult to harm the ecosystem in the water.

Therefore, the algaecides with stronger efficacy or longer duration of action are not always the best choice.

Image source: unsplash.com / Cristian Palmer

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