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Especially during the hot season, but also in winter, deposits can appear in the pool basin.

Depending on the color of the deposits, there are different types of deposits on the bottom of the pool, which must be determined in a first step. Assuming that the respective debris is already present on the pool floor, the following sections will also address how to remove it most effectively.

Furthermore, even before the first colored deposits appear, but also after they have been removed, it is advisable to take preventive measures so that they no longer occur, which is why they are also addressed in the following text sections.

Green deposits on the floor

Conspicuous green deposits on the walls or the bottom of the pool are so-called green algae, which are very common in comparison.

The type of algae called by the technical term Chlorophyta is characterized by a slimy consistency, and in the vast majority of cases it gets into the pool water from water polluted with algae with the help of bathing suits as well as toys.

There, insufficient filtration or too low a dosage of the appropriate agent used for disinfection are often the cause of strong growth, which shows itself in green deposits on the bottom and walls of the pool.

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Remove green deposits in the pool

Once you have determined the green deposits as the particular type of algae, a first step to eliminate the color pollution is to disinfect both the pool accessories, as well as clothing such as swimsuits accordingly, so that no new infestation of green algae can occur.

Then it is necessary to determine at least the values of chlorine content and the level of alkalinity as well as the pH value, so that these can be corrected if necessary, before the existing algae by the use of a brush or by a manual suction to a large extent to suck off.

Then, with a double dose of a pool shocker, a so-called shock chlorination is carried out, which disinfects the water of the pool before starting the filter pump for at least eight hours.

Once this is done, the green deposits are again scrubbed off, which is completed by shock chlorination with a single dose of the pool shocker. Last but not least, do not clean the filter at all by rinsing it out, but with the help of filter cleaner and perform another pool chemistry check before jumping into the cool water again.

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Prevent green deposits in the pool

There are a few ways that you can significantly reduce the risk of green deposits forming on the bottom or walls of your pool. Apart from cleaning the pool accessories at regular intervals, the addition of an algaecide after cleaning, as well as an ideally balanced chemical composition of the pool water, serves as a preventive measure.

It is also extremely effective to operate the filter system pump between eight and twelve hours per day, to repair the smallest cracks in the pool promptly to prevent algae from attacking it, and to perform shock chlorination approximately every other week for basic cleaning.

Red deposits on the bottom

If no green, but rather a pink or red slimy film forms on the walls and the bottom of the pool, so-called red algae, also called “pink slime” in the English language, are present.

However, this is by no means a specific type of algae, but contrary to the misleading name suggests, a biofilm consisting of bacteria, which is initially colorless and only on contact with a disinfecting chemical due to the death process take on the characteristic pink color.

The proliferation of bacteria, which, by the way, do not pose any risk to human health, is often due to unfavorable weather conditions, a disinfectant in too low a dosage, insufficient maintenance of the pool, or a combination of the above.

Removing red deposits in the pool

In order to efficiently remove the so-called red algae, it is essential that the chemical properties of the water in the pool have ideal values, which is why the first step is to check the alkalinity, chlorine content and pH value on the one hand, and correct them if necessary on the other.

Afterwards, the pool is cleaned of red deposits by brushing them off with an appropriate pool brush, sucking off the remaining components with the help of a manual pool vacuum cleaner, for example, and then backwashing the respective filter system, as the bacteria will otherwise continue to multiply there.

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As soon as the water of the pool and the materials of the pool have been disinfected from scratch by a triple shock chlorination, a 24-hour start-up of the filter system with an added filter cleaner follows, as well as a renewed backwashing of the same and, last but not least, a check of the existing chemical means for pool maintenance, in which the chlorine content should be above 1.5 ppm (parts per million or milligrams per liter).

Prevent red deposits in the pool

Due to the fact that the removal of red deposits is not only very time-consuming but also very labor-intensive, it is worthwhile in most cases to take preventive measures so that it does not even come to a multiplication of the bacteria in the respective pool.

These include, first, maintaining a chlorine content of between 2 and 3 ppm (parts per million or milligrams per liter) to ensure the disinfecting effect, as well as cleaning the pool walls and bottom at regular intervals with the help of a pool brush or pool vacuum.

Especially if you plan to go on vacation, it is advisable to hire someone to supervise the pool or, set in case this is not possible, add a high amount of chlorine to the water.

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Yellow deposits on the bottom

If you find yellow deposits on the walls or the bottom of the pool, the pool is inhabited by so-called mustard algae, which have a golden yellow color.

Unlike the name suggests, the organisms known as xanthophytes are not algae in the conventional sense, but belong to the family of molds, which are also very rarely found in domestic pools.

Due to the fact that, compared to green and red deposits, on the one hand they are resistant to the chemical chlorine used for disinfection, and on the other hand the ability to survive outside the water of the pool, those organisms are particularly stubborn.

Removing yellow deposits in the pool

In order to ensure that the pool is not only temporarily free of yellow deposits after the following steps, but that this fact is established as a permanent condition, it is essential to efficiently remove the mustard algae from every object, including swimsuits and other pool accessories.

Before testing the chemical composition of the pool water and then correcting, above all, a less than ideal chlorine or pH value or an unsatisfactory alkalinity, the pool must be freed of the yellow deposits with the help of an adequate pool brush, which are then vacuumed off.

In order to remove this type of algae as well, due to its resistance to chlorine, a threefold increase in the dosage of this chemical is required in a shock chlorination by a pool shocker, which is supported by previously brushing the surfaces of the pool again.

After that, both the filter and the corresponding pool pump are put into operation for 24 hours until the yellow deposits have disappeared, which is ensured by additional brushing and another check of the pool chemistry before a second shock chlorination, which, however, is carried out only with a single dose of pool shocker.

After inspecting the chemical properties of the pool water one last time and finding no noticeable changes, the pool in question can be considered free of the yellow algae.

Prevent yellow deposits in the pool

In order to prevent the reappearance of yellow deposits in the pool at an early stage, a number of preventive steps can be taken, including regular disinfection of swimsuits and pool accessories and toys, especially if they have previously come into contact with foreign water.

Furthermore, shock chlorination should be carried out at least once a week after nightfall, whereby it is also important to ensure that the pool chemistry values are ideally adjusted. In combination with an ideal value in terms of chlorine content, alkalinity and pH value, it is also important to subject the components of the pool to a basic cleaning at regular intervals.

Black, gray or brown stains in the pool.

Due to the fact that black, gray or brown stains in the pool have a variety of causes, the methods to remove or prevent these colored deposits differ in part.

Gray or black stains are often caused by metallic deposits such as brass, bronze or copper. Brown discolorations, on the other hand, indicate either an organic cause, including leaves and dead insects, or an occurrence of iron oxide, which may also be the deposit of fatty substances.

Remove black, gray or brown deposits.

If the deposits are caused by metallic components, the process of removing them is extremely long and involves an initial shock chlorination in combination with setting the ideal pH value, then adding a flocculant and a metal neutralizer according to the individual dosage instructions, reapplying the neutralizer after four days and backwashing the filter system on the seventh day, which should take about 10 hours.

Organic stains are the easiest to remove, as only a little chlorine is needed for this purpose, whereas if greasy deposits appear, the only thing to do is to replace the respective component.

If, on the other hand, the brown stains are due to the presence of iron oxide, for example, it is also advisable to carry out shock chlorination and to use a metal neutralizer and a flocculant, or to replace possible components that corrode.

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Prevent black, gray or brown deposits

The occurrence of colored deposits caused by metal can be prevented by the choice of pool water, as well water should be avoided due to the increased risk, and in some cases it is advisable to add a flocculant or a metal neutralizer to the water at regular intervals and to check the properties of the pipes.

Organic brown deposits can be prevented very easily in comparison, since among other things the use of a landing net, the use of a tarpaulin or also the use of a pool vacuum cleaner can often be helpful here, depending on where the stains are located.

If, on the other hand, you want to prevent brown deposits, which can be caused by body lotions, among other things, in addition to a thorough shower before spending time in the pool, a regular cleaning of the water line combined with the use of edge cleaners is recommended.


Depending on what kind of deposit it is, it can be caused by various reasons, apart from algae or bacteria, for example, metallic particles on the surface of the pool, which may require time-consuming and labor-intensive removal.

In the event that you do not want to remove pool deposits from the bottom of the pool in the future, it is essential to take appropriate preventive measures, depending on the cause of the colored deposit.

With a balanced pool chemistry as well as a manual cleaning at regular intervals, however, the best conditions exist for a future carefree bathing pleasure in one’s own pool.

Larry has been a true water rat since childhood. Pure pleasure turned into a passion. That's why he is the first point of contact for friends and acquaintances when it comes to pool-related problems. He is an integral part of the PoolHandbook editorial team.