When Mold Forms In Hydroponics – Here’s How To Deal With It

Hydroponics is considered to be a particularly easy way of keeping plants, as the watering intervals are far apart in time. However, too high humidity can become problematic, for example, because it often leads to mold growth in the pot.

Weißer Belag auf der Hydrokultur: Ist das Schimmel?

Hydroponics can not tolerate water indefinitely

Before treating your plants, check to see if the apparent mold is really a fungus. Expanded clay tends to effloresce when combined with water, forming a whitish crust. However, it is quite natural and not at all a cause for concern.
You can also over water a hydroponics system if mold forms on the surface, so react first by reducing the water level.
Excessive humidity is a common problem. Be sure to vigorously ventilate your living space or plant location on a regular basis so that humidity levels can regulate optimally.

If the infestation is small, simply replace the top layer of expanded clay with a fresh layer.
If expanded clay contaminated with mold spores remains in the pot, the risk of a new infestation is very high.

How to get rid of mold

You should dispose of very heavily infested plants. For less severely infested plants, it is worth replacing the expanded clay completely so that the plant can recover. However, to do this, it is absolutely necessary to eliminate the reason for the mold infestation beforehand, for example, lower the humidity. Additionally, wash the plant root thoroughly and place it in a one percent copper sulfate solution for 12 hours.

Mold always forms where there is too much moisture. Choose a warmer location for your plant. There, the moisture on the surface can evaporate more easily, preventing mold from forming. On a cool surface, on the other hand, condensation forms, which promotes the formation of mold.

Hydroponics and mold

Hydroponics is a special way of keeping plants. In hydroponics, the plants are kept in an inorganic substrate.

Hydroponics is all about water and moisture. Therefore, mold is an important issue.

Mildew is especially likely to form in damp places. There are many different types of mold, some benign (even edible) others extremely dangerous.

For many plants mold means death, especially if the roots are attacked, there is hardly any rescue.

Hydroponics are very vulnerable to mold if not properly cared for.

Like all plants, hydroponics should not be overwatered. There are special meters for the ideal water level/humidity. If there is too much water, you should reduce the water level immediately.

High humidity favors the formation of mold. Therefore, you should regularly ventilate the plant location to regulate the humidity.

Substrates that are made of expanded clay often tend to blow out when they come into contact with water, this creates a white crust, this is often mistaken for mold.

If your hydroponics or any other plant is affected by mold, you must react immediately.

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You should immediately dispose of a plant that is already heavily infested.

For less severely infested plants, you should replace the substrate immediately. Wash out the root carefully. To wash out, place the plants in a one percent copper sulfate solution for about 12 hours.

Since mold forms where it is moist, so you should choose a warmer location. The warmer the location, the better the remaining moisture can evaporate.

However, make sure that there is no condensation, this would again provide too much moisture and promote mold growth.

Since mold collects in the substrate you should regularly renew the substrate so that the fungi can not spread.

Where and how is the mold formed?

First of all, mold spores are everywhere, including in the air around us. Mold develops when these mold spores are able to settle. In order for mold to grow, favorable growing conditions are essential. Several factors are indispensable for this.

The most important factor is humidity. Wherever a certain basic humidity prevails, mold will grow. This cannot be avoided in hydroponics. As a tip, when watering the hydroponically cultivated plants, you should pay attention to possible beginnings of mold as well as to the indications of the water level meter. Please do not forget that hydroponics can also be overwatered.

Another point that is indispensable for mold is the presence of organic material that it can metabolize as food. A source of this food are, for example, discarded drinks such as coffee, tea, sugary sodas and so on. Also other organic material like food leftovers as fertilizer substitute have no place in hydroponics. Also soil residues in an unprofessional hydroponics are a good breeding ground for mold.

Other factors of mold growth are time. Mold needs time to develop. Therefore, you should regularly look for mold deposits and, if necessary, change or clean the granules.

The pH of the water also plays an important role in the formation of mold. Here, make sure you have the right pH level that suits your plant.

The next point is oxygen, which mold needs to develop and grow. This is often found in air chambers if you have created your hydroponics improperly.

The last point is heat, which mold needs to grow. Of course, the plant itself usually needs heat as well, so make sure you have it not too warm and not too cold. Therefore, for tropical plants, you need to change the substrate more often or washing.

The problem is that the parameters and factors that favor mold are given quite quickly or are unavoidable. Therefore, good care of your plants in hydroponics with regular checks is essential.

If you keep hydroponics these factors in mind and check and maintain them regularly, you can minimize mold growth to a large extent. Do not leave your hydroponic plants in a very wet container for an extended period of time. Do not add organic material and pay attention to environmental factors.

What to do if mold has formed?

If mold has formed or is forming, you can proceed as follows. You will need one percent copper sulfate solution.

If the plant is already heavily infested with mold, you should dispose of it. Save it is unlikely, but you can try.

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Mold always forms where humidity is too high.

Check, the air humidity and determine the cause of the mold. Only when the cause is eliminated should you take further action.

If the humidity is too high, lower the humidity. For example, by moving the plant to another location or by “optimizing” the ventilation around the plant but without putting the plant in a drafty area. For example, there are gel beads that you know from shoes or other products that absorb humidity. Similar products are also available for hydroponics.

If there is too much water in the planter, reduce the water content. Use a hygrometer for this purpose. You can find this in specialized stores. In our articles on clay and clay granules above, you will find an overview of various hygrometers we recommend especially for hydroponics.

For example, choose a warmer location so that the moisture can evaporate better. Pay attention to whether condensation forms somewhere. The is the case on cool surfaces. This water can then flow back to the plants, for example.

When you have eliminated the cause, proceed as follows:

First, remove any mold, replace the expanded clay completely. Then, wash the plant roots thoroughly and place the plant roots in a one percent copper sulfate solution for at least twelve hours.

It It mold or something else?

If a white coating appears on the expanded clay balls in the hydroponic container, some hobby gardeners immediately think of mold.

In fact, however, it is not rotting fungi, but only salt efflorescence, explains the Central Horticultural Association (Bonn). Salts from both tap water and fertilizer are deposited on the surface. Both are completely harmless to plants, humans and animals.

Whether efflorescence occurs or not also depends on watering. If water is poured only to the optimum mark on the water level indicator, the moisture usually does not rise to the surface of the pot. Efflorescence then takes place below the surface and is not openly visible. If, on the other hand, the pot is always filled up to the maximum mark, which actually only indicates the water level for bridging longer absences, globules on the surface will also be soaked, and salts will effloresce.

Once this happens, the top layer can be easily replaced with fresh expanded clay beads.

White coating on hydroponics: is it mold?

The brown beads for hydroponics of houseplants sometimes turn white. Is this mold? What are the advantages of growing plants in hydroponics rather than in ordinary potting soil? Here you will learn interesting facts about expanded clay.

Plants don’t necessarily need potting soil to grow healthy. Most thrive magnificently in hydroponics, a natural substrate made of baked clay pellets. However, when a white coating gradually appears on the hydroponics beads, many amateur gardeners automatically think of mold.

In fact, the white coating on the hydroponic balls for indoor plants is completely harmless. No mold can develop on the expanded clay balls, since the substrate is not organic material.

The white deposits are only salt remainders from the nutrient solution, which are added to the watering water with this form of the plant irrigation. These are however healthwise completely harmless, why house plants in hydroculture may be used also in medical practices and hospitals, explain the expert.

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Hydrokultur hat einen großen Vorteil: Es ist optimal für Allergiker.

How can the white coating on hydroponics be removed?

If you are bothered by the coating, you can wash the top grains of the substrate. If there are only small amounts of salt on it, Helk says it can be enough to rinse the balls with the irrigation water.

What actually is hydroponics?

Hydroponics plants do not grow in the soil, but in a special mineral expanded clay substrate. The clay balls are a natural product. They are fired at around 1,200 degrees, during which they change their volume and become larger. The result is “a grain with a stable outer skin, which has a core inside with fine pores and air holes,” the trade association explains.

The spheres are usually not round, but mostly kidney-shaped, which is due to the manufacturing process.

The advantages of hydroponics

The clay pieces store water and slowly release it to the plant. That is, you need to water the plants much less often.
Neither waterlogging nor fungal diseases can harm the plants.
There is usually a water level indicator on the pots that shows amateur gardeners when their plant needs water again.
If the pot has an additional water reservoir in the bottom of the pot, your plants will be well supplied even on vacation: if a water reservoir is installed, your plant can supply itself for two to four weeks.
The substrate weighs less, so it’s good for large pots that need to be moved.
Hydroponics is ideal for allergy sufferers as it does not allow fungal spores to form. This makes it well suited for doctors’ offices and hospitals.

The substrate does not need to be replaced, so plants only need to be repotted if they need a larger pot.
Actually, all plants thrive in the substrate made of clay pellets.

Disadvantages of hydroponics:

Hydroponic plants are usually more expensive than plants in potting soil.
Hydroponics cannot store nutrients. Therefore, the plants need to be fertilized regularly. It is best to fertilize hydroponics plants with special hydro fertilizer.
If you have children or cats, you often face the problem that the pellets spread throughout the apartment.


  • James Jones

    Meet James Jones, a passionate gardening writer whose words bloom with the wisdom of an experienced horticulturist. With a deep-rooted love for all things green, James has dedicated his life to sharing the art and science of gardening with the world. James's words have found their way into countless publications, and his gardening insights have inspired a new generation of green thumbs. His commitment to sustainability and environmental stewardship shines through in every article he crafts.

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