Water Culture Hydroponics

Water Culture hydroponic systems are the second easiest systems after the Wick Systems. Their principle of operation is quite simple and relatively inexpensive to set up, so ideal if you are just starting exploring hydroponics.

ProsCons
Simple in set-up. Simple and relatively inexpensive materials. The only moving part is the air pump plus the water pump if you go for the “expandable” formConstant aeration of the nutrient solution is required because the roots are submerged in it
Can be used for all plants, fruit-bearing ones includedCalibration of the nutrient solution can be tricky if done with the roots in the solution. A sudden change caused by a mistake in the nutrient concentration or pH can damage the plants
Maintenance is easy and inexpensive. Just make sure the aeration is constantly in operation and that the reservoir and tubes are clean.Water temperature is important to be kept within a range in order to have the right amount of dissolved oxygen in the solution
Little experience required 

 

Although it is recommended for all levels of experience, it can be used even if you plan to go larger scale in almost any type of plant cultivation; it is also largely used by commercial-scale plant production for fruit and vegetables.

The set-up

It is rather simple. As its name reveals, the plant roots are suspended in the nutrient water solution, while the plant is supported by cups containing the growing medium.

In its simple form, the cups holding the plants are placed on the nutrient solution container itself; either in holes on the container lid or in holes in Styrofoam cap on the container.

In its more “expandable” form, the main characteristic is that the solution is recirculated. The solution container is separate from the buckets which house the growing medium and the plants.  The solution container is connected to the plant buckets with hoses/tubes that transfer the nutrient solution to the bottom of each bucket; physically the same water level is maintained in all of the buckets.

In either form, the simple or the “expandable” one, there is a need for aerating the nutrient solution and this is most commonly done with an air pump that pushes air through a hose/tube to an air stone in order to create small bubbles of air. The air stone can be a simple one used for ponds.

In the “expandable” form, a water pump is required to push the solution from the main reservoir to the individual buckets in, most commonly, a series arrangement. Water is constantly moving from the main reservoir to the first bucket, then the second and so on, until the overflow from the last one gets back to the main reservoir.

You can have more than one of those branches out of the main reservoir.

What you will need

  • A large nutrient solution container – this needs to have a flat lid if used as the main plant-holding structure or it can be a round barrel if it is used in the “expandable” form
  • Air pump with air tube and air stone (for both the simple and the “expandable” forms)
  • Water pump to circulate water (for the “expandable” form)
  • Timer for the pump
  • Hoses/tubes to transfer the water from the main reservoir to the individual buckets (for the “expandable” form)
  • Growing medium
  • Baskets to hold the plants
  • Individual buckets for the “expandable” form to house the baskets and the nutrient solution
  • PH sensor
  • Electrical Conductivity (EC) sensor (measures the total salts in the solution)

Aeration

As the roots are placed directly above and are largely submerged into the solution, there is no need for a water pump; however, the solution needs to be aerated. Roots need oxygen for a healthy and fast-growing plant (oxygen is a stimulating growth factor). Aeration is achieved by a simple air pump connected to an air stone via tube(s). The smaller the bubbles coming out of the air stone the better, as the contact surface area with the surrounding water is larger and the effectiveness of dissolving oxygen is higher.

For even smaller bubbles you can use a soaker hose (normally used for irrigation), you would need to have a couple of loops at the bottom of the solution tank to allow for sufficient air to come out.

The aeration follows the same technique in any set-up you may choose for this type of hydroponic: in the “expandable” form aeration is done in the main reservoir and the recirculated solution is aerated.

Water level

It is important to note that the roots should never been left to dry out. In any case, always leave around 1-2 inches (5cm) between the water level and the root crown to avoid root rotting. The moisture in the growing medium will be enough to moist that top part of the root.

Where the water level should be in relation to the baskets (which hold the growing medium and the plants) depends on a combination of parameters:

  • Growth stage. When the plant is still small, the roots are not long and if the basket is large they are unlikely to have come out of the bottom of it. So the basket may need to be submerged into the solution by a couple of inches (5cm) in order for the solution to be absorbed by the growing medium and reach the roots.

If the plant is larger and the roots have come out of the bottom of the basket, then make sure that the roots are submerged in the solution. Depending on the size of the basket, it is likely that part of the basket needs to be submerged as well, but always ensure that you leave a couple of inches below the root crown above the water level.

  • Growing medium. If the growing medium is not absorbent enough, then you need to increase the water level by adding some volume in, or change to a more absorbent growing medium. If on the other hand the growing medium is super absorbent, lower the water level by removing some volume of solution out so that it just touches the baskets.

Remember! Each time you add water to increase the water level, you need to make sure that nutrient concentration is the right one, pH and EC indications are within the set range suitable for the specific plant at its current growth stage.

  • Aeration force. If the aeration is quite forceful, i.e. the bubbles are too many and their speed too high, the nutrient solution will be like boiling. The bubbles will be rigorously popping on the surface will form droplets, quite many of them reaching a height of up to 2 inches (5cm) above the water level. In that case, you may want to consider not submerging the baskets in the solution because the droplets may be enough to gradually moist the growing medium which will transfer that moisture upwards.

Typical Problems

Algae, bacteria and other microorganism growth in the solution. Avoid using transparent containers/reservoirs where light can pass through. Light encourages microorganisms to grow which can change the chemistry of the solution, reduce the efficiency of water and oxygen absorption by the roots which can lead to root rotting, ultimately reducing yield.

Thirst. If you notice that your plants show signs of thirst or the growing medium is not wet enough, then try the following one by one:

  • Check if the water level is too low and the roots are dry – worth checking regularly for changes in the pH and EC indicators that will indirectly tell if water volume has gone down.
  • Add more water in the solution but ensure that the nutrient concentration is as it should be and if required recalibrate.
  • Change the growing medium to something more absorbent.
  • Ensure that the water level in the solution container is filled up and remains high regularly.
  • Check if the water pump (for the “expandable” form) works and that there are no water leaks and that there is recirculation of water as expected

Oxygen starvation. When roots do not get enough oxygen, they can be damaged and die. Early signs can be leaves that become wilt, distorted, or not growing to their expected size. Past that level, the leaves can yellow and drop. If the condition is not taken care of, the entire plant can wilt, stems will start dying and the entire plant will eventually die.

If you have observed these signs, try the following one by one:

  • Check that the air pump works and that bubbles come out of the air stone
  • If the air pump works but little or no bubbles come out of the air stone, check for any air leaks along the tubes and joints
  • If bubbles form, check if the roots are dry which then is a problem of thirst.

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