It is often read, but not everyone knows what to do with the term “hydroponics”. The word, derived from the Greek, describes the cultivation of plants of all kinds in water. The advantage of this attitude is obvious: the constant availability of water means that the usual watering process is no longer necessary and the hydroponic indoor plants can be forgotten even for a short time. However, it is wrong to assume that hydroponics does not require any maintenance. Regular fertilization of the plants as well as cleaning of the substrate must nevertheless be carried out.

What is the substrate made of?

Hydroponics consists of an inorganic, lime-free substrate. Only the composition and graininess vary depending on the material chosen:

  • Basalt – The outflow rock formed from volcanic activity is also used in hydroponics. The dense structure of the basalt gives the root network of the plants a secure hold.
  • Perlite – Another rock whose origins can be traced back to volcanic activity. The great advantage of perlite is that it can bind larger amounts of moisture and nutrients.
  • Gravel – The use of gravel is also not uncommon in hydroponics. However, this substrate is relatively heavy and a special electric pump is required to supply the plants with water. As with sand, the gravel must be sufficiently cleaned before it is used for the first time.
  • Expanded clay – The baked clay balls are among the widespread classics among hydroponic substrates. The light material can also be used for sensitive plant roots due to its low weight. Expanded clay is easy to clean and sterilize.
  • Mineral wool – This substrate – also known as rock wool – distributes nutrients and water evenly in the culture vessel. The relatively light material is also suitable for growing young plants and keeps harmful pathogens away from them.
  • Styrofoam Flakes – These special Styrofoam flakes are light in weight and relatively inexpensive. Nevertheless, they are rarely found in conventional hydroponics.
  • Sand – Cultivation with sand is also possible in hydroponics. However, due to its low storage of moisture and the density of the soil, this substrate is more suitable for succulents with low water requirements.

Other commercially available hydroponic substrates include coconut fiber, broken brick, diahydro and vermiculite. Which material is most suitable for you depends on the specific needs of the plants chosen and the purpose of hydroponics. If you are unsure how to use hydroponic fertilizers, you can also use a special nutrient solution for cultivation.

Hydroponics plants

The right plants and the ideal location

There is hardly a plant that is unsuitable for hydroponics. The cultivation in the inorganic substrate stimulates the plants to develop special “water roots”. These are far less branched than the normal earth roots and can therefore tolerate larger amounts of moisture much better. Root rot and other diseases caused by waterlogging are relatively rare in hydroponics.


Universal fertilizers, fertilizer sticks or other commonly used fertilizers are hardly or only partially suitable for hydroponics. However, the inorganic substrate of hydroponics is not able to deliver important minerals to the cultivated plants itself. Just like the water storage tank, special hydroponic fertilizers must therefore be refilled every quarter to six months.

  • Liquid fertilizer for hydroponics – as with conventional cultivation in soil – is added to the irrigation water according to instructions.
  • The tablets of long-term fertilizers are placed directly in the water reservoir and secrete important minerals over a period of several months.

Repotting from and in hydroponics

Hydroponics Repotting

Due to the lush growth, the hydroponic plants also need a larger culture vessel at certain intervals. There are different ways to repot.

The specialist trade has many special vessels for hydroponics ready. As a rule, however, all watertight vessels are suitable for this type of cultivation. Caution is advised with conventional cachepots, as these often cannot hold moisture permanently and at some point unsightly water marks appear on the surfaces.

  • Avoid metal vessels and glazed planters.
  • Two vessels are required for smaller plants – an inner pot and a waterproof planter.
  • The water level indicator with the float is attached in the inner pot. Special hydroponic vessels have a separate shaft for this.
  • Larger plants can do without inner pots.
Tip: Only use special inner pots for hydroponics, as these have all the necessary openings for the roots and water.

Repotting hydroponic plants differs only slightly from plants in conventional soil:

  • Carefully remove the inorganic substrate from the plant.
  • When the roots have completely penetrated the planter, carefully remove them from the pot.
  • In the larger inner pot, create a drainage from a thicker layer of the hydroponic substrate used. This prevents the roots from being in direct contact with the water.
  • Carefully place the plant in the new container and fill it up with new substrate.
  • For a better distribution of the hydroponic material, the pot should be regularly placed lightly on a firm surface.
  • As soon as the inner pot is connected to the outer pot, it is filled with lukewarm, lime-free water. – The float of the water level indicator may rise to the maximum mark.
  • Depending on the type of substrate, it is possible to reuse the previously used hydroponic material. Expanded clay, for example, can be easily cleaned and sterilized in white wine vinegar.

Repotting soil in hydroponic plants: Many types of plants are suitable for hydroponic cultivation. It is up to you whether you want to cultivate it directly in inorganic material or use a hydroponic plant from specialist retailers instead. However, it is much more difficult to convert older plants from conventional soil into hydroponics. Because if even the smallest amount of organic substrate remains on the roots, this can lead to fungal diseases and root rot.

  • Whether young or old plants are irrelevant when converting to hydroponics. The plant must freshly develop the entire root system for the new cultivation.
  • Roughly remove the soil and shower the rootstock with lukewarm water. Repeat this process until no more soil sticks to the plant.
  • A drainage from hydroponic substrate is prepared in the inner vessel as standard.
  • Insert the plant and slowly and carefully fill it up with the new substrate.
  • Make sure that the hydroponic material is evenly distributed by knocking on the vessel and pressing it lightly.
  • Provide plenty of lukewarm water – however, the swimmer must not reach the maximum level.
  • Only when the plant has developed its new roots – a change that can take several months – can it be treated like any other hydroponics.
  • Do not change location in the first few months so that the plant can acclimatise without any problems.

The plants do not always survive the changeover without any problems. Deficiency symptoms and caring shoots are not uncommon at first, because the plant changes its entire root system from soil to water.

Growing in hydroponics

Hydroponics is not only suitable for indoor plants, but can also be used for growing them.

  • The substrates perlite, expanded clay and mineral wool are ideal for growing seeds.
  • The planter must be light and warm – a room temperature between 20 – 24 ° C is ideal.
  • The seeds are not allowed to swim in the water. A water level of a few millimeters is better.

Care and cleaning

Hydroponics Care and cleaning

One thing may be true: plants in hydroponics are easier to care for and require fewer watering intervals than indoor plants in conventional potting soil. However, hydroponics cannot be left entirely to their own devices. For example, the substrate used must be checked and cleaned at certain intervals.

  • Once a year, clean the substrate and the plants with lukewarm water. Fertilizer residues and foreign substances that have penetrated can be rinsed out with a gentle jet of water.
  • The plants are also cleaned in this way.
  • Tpp: Some hydroponic substrates – such as expanded clay, for example – can be sterilized by taking a long bath in white wine vinegar.
  • Regularly remove foreign matter such as cigarette butts and dead insect bodies from hydroponics.
  • Choose a bright location for the plant.
  • The place directly above or next to radiators is unsuitable and only recommended during the cultivation phase.
  • Do not always top up the water level to the maximum level – this has a positive effect on the life expectancy and growth of the plant.
  • Any kind of leftover drink has no place in hydroponics.
  • Regularly cut off brown shoots and wilted leaves before these organics get into the inorganic substrate.
  • If a putrid smell penetrates from the inside of the pot, there could be root rot. Check the plant and change the entire substrate if necessary.
  • Conventional fertilizer for house plants is only suitable for hydroponics to a limited extent. Pay attention to the additional note “for hydroponics” or use special fertilizers directly.
  • The substrate is susceptible to bacterial and fungal diseases. Frequent visual checks and regular cleaning of the hydroponic material, the pots and the plant is therefore advisable.

Possible maintenance errors

Hydroponics does not mean that the plants can be left to their own devices. The sensitive system can tip over quickly through improper handling and diseases and pests do not stop at indoor plants in hydroponics.

Plant gets brown leaves:

  • The location is too dark or the plant is exposed to direct sunlight.
  • Some indoor plants require high humidity even in hydroponics. Spray the leaves and shoots more often with lime-free water.
  • Too much water damages some plants – put them in regular dry phases.

Yellow discoloration on shoots and leaves:

  • Plants in hydroponics generally need a lighter location than in conventional soil cultivation.
  • Too little or too much fertilizer was used. Fertilize immediately or clean the plant and the substrate extensively with lukewarm water.
  • Never pour over it – water does not always have to be topped up to the maximum level.
  • Too dry room air or being in close proximity to radiators can also lead to discoloration.
  • The water is too hard. If possible, use stale rainwater.

The plant visibly cares:

  • The selected inner pot may be too small. In this case, move the plant to a larger inner container.
  • Were the plant’s roots damaged during cleaning or repotting? Remove the entire, injured root cord and water only moderately over the next few weeks.

There are many reasons for purchasing or switching to hydroponics. Whether as a decorative eye-catcher in the office, as a useful air humidifier in the living room or simply to keep the maintenance of indoor plants low – with hydroponics, a number of possible uses can be implemented.

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