What Is Deep Water Culture? (And How To Build One)

You want to grow vegetables and herbs without soil and with simple means? Then the deep water culture of hydroponics is just the right hydroponic system for you!

A hydroponic deep-water culture is easy to maintain, high-yielding and quick to build.

Therefore, you will now learn everything important about the hydroponic system, so that you can build your own system quickly and easily yourself.

What is deep water culture?


Deep-water culture is an active hydroponic system in which the roots of the plant are suspended in a nutrient solution. Thus, the plant is supplied with water and nutrients at all times.

The plants are in net pots and are fixed with a substrate.

The net pots can be placed above the water surface in two ways: either holes are drilled in the lid of the water reservoir or the net pots are placed in a floating platform.

The latter option has the advantage that the roots are always surrounded by the nutrient solution.

Advantages


Deep water culture is one of the simplest hydroponic systems. In this system, the roots have optimal access to water and nutrients. That’s why vegetables and herbs grow quickly and efficiently.

Three advantages make deep water culture so popular:

low maintenance
fast and easy to build
very efficient and high yield
Because of these advantages, the system is very suitable for beginners and advanced growers.

Disadvantages


Where there are advantages, there are also disadvantages.

The hydroponic system

tends to lack oxygen and
is not suitable for every plant.
Because the nutrient solution does not circulate in the system, oxygen does not get into the nutrient solution. The oxygen in the water is absorbed by the roots over time. Since too little oxygen causes the roots to rot, the plant can die as a result.

Fortunately, with the help of a pond or aquarium air pump, the danger can be averted: the air bubbles enrich the nutrient solution with oxygen and promote growth.

Build your own deep water culture


You now know how the system works and what the pros and cons are. Great! With that, you’re ready to build your own deep water culture. Now it’s time to get down to the nitty gritty.

For the basic deep water culture system you will need:

  • A water reservoir,
  • net pots,
  • substrate,
  • a floating platform/lid and
  • an air pump (optional).


So far so good. Before you start, however, consider the following tips:

The water reservoir

Tiefwasser-Kultur in Box

Nothing beats a sturdy water reservoir.

The best option is a simple box with a lid. Holes can be drilled in the lid and the net pots put inside.

Keep in mind that a filled water reservoir can become very heavy. Therefore, fill it in the designated place and choose a sturdy box. After all, you don’t want to risk flooding.

So that you only have to fill the system once, you should plan on about 5 liters per plant. Likewise, each plant should have at least 20 cm³ of space.

Please note that these are of course only guidelines and can vary depending on the plant.

Also remember to buy an opaque box, otherwise algae will infest the system.

Net pots and substrate

As you already know, the net pots are filled with substrate.

There is nothing serious to consider with the net pots. They should only be sufficiently stable so that they can be reused.

As long as the substrate does not come into contact with the nutrient solution, you can use any substrate in a deep water culture. Note the particle size. If substrate falls into the nutrient solution, it can affect the pH.

Netztöpfe mit Substrat

For a deep water culture of hydroponics we recommend

  • Perlite,
  • rock wool,
  • vermiculite and
  • expanded clay balls.


Of course, organic substrates such as coconut fiber are also suitable. However, particles often get into the nutrient solution.

Floating platform/lid


Styrofoam is most commonly used as a floating platform.

Styrofoam has the advantage of being readily available and having a high buoyancy. Other materials often cannot keep plants afloat in the late stages of growth.

From an ecological point of view, we recommend simply using the lid. This is also made of plastic, but it is much more durable and also cheaper.

Alternatively, a painted wooden board can be placed on the edges of the water reservoir.

The air pump and the air stone


As mentioned earlier, oxygen depletion can occur in a deep water culture. To counteract this, a small aquarium or pond air pump is needed.

Usually, an air stone is included with the purchase of an air pump. This should have as fine pores as possible. The finer the pores, the more oxygen dissolves in the water.

The advantage of such aeration is noticeable in growth and yield. However, make sure that the air pump does not suck in air that is too warm or too cold. Otherwise, the extra air will hinder growth.

Note: An air pump is not absolutely necessary. There are enough gardeners who achieve a high yield in a deep water culture without an air pump.

Troubleshooting


Although deep water culture is a low maintenance hydroponic system, unwanted problems can still occur.

If the roots turn brown or muddy, you should adjust the

  • water temperature and
  • the pH of the nutrient solution
  • check.

If the plants are growing slowly, you should follow these tips:

  • EC level may be too low
  • Plants do not have enough light
  • Water is too cold (temperatures below 18 degrees should be avoided)

Frequently asked questions about deep water culture


Which plants are suitable for deep water culture?


Originally, hydroponic deep water cultures were designed for tomatoes. Therefore, it is also possible to grow large vegetable plants such as cucumbers and tomatoes.

Because fruit plants usually need a lot of oxygen, an air pump is recommended. Due to the heavy weight, a floating platform should not be used.
Only small-growing plants such as lettuce or herbs are suitable for floating platforms.

A selection of suitable plants:


Plants that are very suitable for deep water cultivation: Basil, cilantro, mint, celery, dill, fennel, kale, lettuce, nasturtium, chives, chard, sorrel, watercress, and brown mustard.

Not optimal, but possible are, for example, peppers, tomatoes and strawberries.

You can find more about suitable plants in hydroponics here.

How do I build a water reservoir?


You don’t want to use a plastic box, but build a reservoir yourself? Then buy some wooden slats and screw them together to form a frame. Then you can lay out the pond liner in it. Your water reservoir is ready!

How often do water and nutrients need to be replenished?


As often as necessary.

It is best to fill the system only once at the beginning. Of course, this assumes that the water reservoir is large enough. Water requirements vary depending on the plant.

For leafy vegetables, however, five liters per plant should be sufficient.

If you still need to top up from the nutrient solution, you will need to check the pH and EC again and adjust if necessary.

How big does the raft need to be?


Small rafts can become too unstable for large plants. On the other hand, they are fine for leafy vegetables.

Most rafts are 60cm * 120cm or 120cm * 240 cm. Match the size to the size of your system. There should be as little space as possible between the raft and the system, otherwise too much light will enter the water reservoir.

Indoor or outdoor?


The location depends entirely on light conditions and personal preference.

If you have an indoor system, the plants should be lit with a plant lamp. Without enough light, the plants will not grow despite an efficient system.

If you prefer an outdoor system, be aware of the following: rain can wash out the nutrient solution and change the pH. Likewise, the hydroponic system is dependent on temperature fluctuations and sunlight. Furthermore, the risk of pest infestation is much higher.

If you prefer efficient growth and want to harvest your plants regularly, we recommend that you design your deep water culture as an indoor system.