At some point, aquarists may encounter a brown algae film that appears on the glass, equipment, and decorations, from which even a weekly cleaning does not save: algae returns and returns. This is nothing but colonies of lower plants – diatoms. They can be found both in the “freshly launched” aquarium and in an already established one. It is not worth ignoring the appearance of these microscopic organisms, because in a matter of days they can cover the entire aquarium with themselves.

To get rid of diatoms, first of all, it is necessary to identify and eliminate the causes of their appearance, and if necessary, use special preparations – algaecides.

About algae

Diatoms, or diatoms (Bacillariophyta) – an extensive class of lower plants that are widely represented on our planet. There are both marine and freshwater species. They play an important biological role in nature since they are an important component of phytoplankton and a food source for many aquatic inhabitants.

Diatoms are exclusively unicellular organisms. Their size is 0.75-1500 microns. Their main feature is the presence of an external hard shell, which is a porous shell of silica. It consists of two halves, which enter one into the other. In the process of reproduction, each new cage gets only one half of the shell, the second it completes itself. Thus, with each new generation, the size of plants decreases. Most often in the aquarium, you can find representatives of the genus Navikula, Pinnillaria, and Zimbella.

Despite the great importance in nature, these algae are undesirable in the aquarium. The brown coating that they form strongly spoils the aesthetic perception of the aquarium. Diatoms are not dangerous for fish, at the initial stages of development they also do not bring serious harm to plants. They are easily erased from glasses, scenery, and plant leaves. A characteristic feature is that diatoms “dust” – if you push with your fingers, a small cloud of dust will rise in the water.

In the case of the rapid development of algae, algae becomes black due to the constant build-up of layers on top of each other. In this case, the lower layer of diatom plaque becomes difficult to remove. It seems that the leaves are sprinkled with earth or black sand. At this stage, diatoms already become dangerous for living plants, because dense plaque on the leaves reduces the effectiveness of the most important process for plant life – photosynthesis, which, in the end, can lead to the death of the plant. Diatoms spread so fast that new leaves are instantly affected by them. In addition, diatoms create an excellent “bridgehead” for securing other difficult to remove algae, such as “black beard”.

Diatoms are very rare in herbal aquariums, because higher plants absorb all the nutrients from the water and there is simply nothing for algae to eat. Therefore, they usually are found in freshly launched aquariums with poor lighting (or without it) and artificial decorations, or established aquariums left without proper care.

Why diatoms appear in an aquarium?

In order to get rid of diatoms as quickly as possible, first of all, it is necessary to carefully analyze and eliminate the causes of their appearance. You can bring diatoms with new fish or plants.

Recently launched aquarium

Most often, diatoms appear in new aquariums with an unstable nitrogen cycle. This means that a high concentration of nitrogen compounds – ammonia, nitrite – is found in water.

Small number of living plants
An additional factor is the lack of living plants – natural antagonists of algae.


If diatoms appear in an established aquarium, launched more than 3 months ago, then the cause must be sought in the imbalance. There should be no overpopulation in the aquarium; fish should receive a moderate dose of food. Do not forget about regular water changes and cleaning the soil. It is important to monitor nitrate and phosphate levels using tests.

Water parameters

It is desirable that the acidity of the water (pH) does not exceed 7.5 units. Water temperatures are best maintained at around 25 ° C. Diatoms prefer cooler water (22 ° C). The high content of silicates in water is an important factor for the appearance of diatoms because it is from them that they build their carapace.

Fertilizer surplus

Fertilizers for aquarium plants can also trigger an “outbreak” of diatoms, so you need to monitor their introduction and prevent overdose. This is especially true in fresh aquariums.

Low light

A positive factor for the development of diatoms is poor lighting or its complete absence. In this case, it is necessary to increase the lighting (for example, put an additional lamp). The length of daylight should not exceed 8 hours, and in the slow herbal aquarium you can limit yourself to 6-7 hours. It is best to purchase aquarium lamps or fixtures with a specially selected spectrum for lighting, which will positively affect the growth of higher plants and suppress algae. If fluorescent lamps are used, then periodically they must be replaced with new ones. It is also important to prevent direct sunlight from entering the aquarium.

Medication for fish

Treatment of fish with preparations containing large amounts of copper or iodine can damage the beneficial microflora in the aquarium and inhibit the growth of higher plants, which, in turn, sometimes leads to the appearance of diatoms. It is especially careful to add table salt for medicinal purposes. The high content of sodium ions has a bad effect on higher plants, but algae really like it.

Excess silicates

The high concentration of silicon dioxide (SiO2) in aquarium water, which aquarists call “silicates,” can trigger the growth of diatoms. After all, it is it who is the building material for diatom shells. To accurately determine the concentration, special (rather expensive) drip tests are used.

Watch this video about diatoms in a new aquarium: Be careful this video has SOUND!

Diatoms! Diatoms! Diatoms! | What You Can Expect With Your New Aquascape | Aquascaping

How to get rid of diatoms

The fight against diatoms, especially in the early stages, does not present serious difficulties.

Wait for balance

If algae settled in a fresh aquarium and do not breed very actively, then it is necessary to wait until the moment of establishment of biological balance (usually it takes 3-4 weeks). When the balance returns to normal, the diatoms will retreat. It is useful to use special bio starter preparations (Tetra SafeStart) to start the aquarium, they accelerate the establishment of biological balance. At this stage, only mechanically remove the algae with a sponge or scraper.

Scrape off algae

An important way to combat this is to remove diatoms mechanically: with the help of scrapers, magnets, and sponges, clean the aquarium glass, and the decorations (grottoes, stones, artificial plants) must be removed from the aquarium and rubbed with a sponge under running water.

Buy algae eater

Many species of fish and invertebrates eat diatoms with pleasure. The most successful brown-blooded wrestlers are Gyrinocheilus. For quick disposal, one fish per 50 liters of water will be sufficient. Popular Bristlenose catfishes will be slightly less effective.

Enhance lighting

One of the most effective ways to help get rid of diatoms is to enhance lighting. Diatoms do not like bright light, so adding extra lamps and reducing daylight hours can effectively deal with them. Aquarium light should be 0.3-0.5 W / liter, and the length of daylight should not exceed 6 hours for the duration of the struggle and then no more than 8 hours (in the absence of living plants). It should be direct because diatoms like diffused and reflected light. It is very important to choose the right color temperature of light sources. “Yellow” lamps should be avoided, it is preferable to use neutral white light lamps (6000-6500 K). In the case of using this method, it is necessary to strictly monitor the content of nutrients in the aquarium, because bright lighting, helping in the fight against diatoms, can trigger the growth of other algae – green algae. It is very important that direct sunlight does not fall on the aquarium.

Adjust balance (nitrates and phosphates)

In order to balance macrocells in an aquarium, you first need to find out their level, for which water tests for nitrates (NO3) and phosphates (PO4) are done.

If the concentration of nitrates exceeds 100 mg / l, this is a critical level; it must be reduced to 50 mg / l, for which 10% of water is replaced 3 times a week.

Next, it is necessary to ensure that the concentration of nitrates is reduced to 20 mg / l, and phosphate does not exceed 0.5 mg / l. The overestimated values ​​of these parameters are often caused by overpopulation in the aquarium or regular overfeeding, so these two factors must be excluded first.

Always ensure that the number of fish in the aquarium matches the volume. The minimum recommended volume of the aquarium for each species is individual, this information can be clarified in the reference materials. For a quick assessment, you can use the rule: for every centimeter of fish for small species there should be at least one liter of water, and for large species – at least two to three liters.

Overfeeding is also a common cause of imbalance in the aquarium because fish that eat a lot produce more waste. It is necessary to feed the pets 2-3 times a day in small portions, which will be completely eaten in a few minutes. If there is a lot of feed left, it is advisable to collect it using a net or a soil cleaner – during decomposition, it can also cause the growth of nitrates and phosphates.

To safely reduce the level of nitrates and phosphates in the aquarium, use the following preparations:

Tetra NitrateMinus – 2.5 ml per 10 liters of water weekly;
Tetra PhosphateMinus – 10 ml per 40 liters of water every other day until you reach the required parameter value.
To comply with the dosage, we recommend using a dispensing cap. It is necessary to provide aeration in the aquarium so that cloudiness does not occur.

Apply Tetra AlguMin Plus and Tetra AlgoStop depot
In addition to normalizing the conditions, it is recommended to use special drugs to combat algae.

A great choice is Tetra AlguMin. The active substance in this algaecide is monolinuron, which effectively fights against various types of algae, while it does not inhibit biofiltration and does not harm snails and shrimps in recommended dosages. Tetra AlguMin starts acting instantly.

In difficult cases, after 7 days, add Tetra AlgoStop depot tablets – After placement in the aquarium, the tablets do not dissolve, but the active substance is released slowly over the course of a month, allowing you to effectively fight algae.