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The Kratky Method - How to Grow Food The Passive Hydroponic Way

Submitted by max on Wed, 07/12/2017 - 01:51

If you have ever known about Hydroponics, basically there are 6 types of Hydroponic systems, namely the Wicking, Deep Water Culture, Nutrient Film Technique, Ebb & Flow, Drip, and Aeroponics. 
Any other types can be just a variation of these systems. 

That's true. 

And today I'm going to share with you an incredibly interesting type of Hydroponic system. It is very easy to set up and use, and obviously a great starter for anyone new to Hydroponics.

Enter the Kratky Method.

What is the Kratky Method? 

This method is discovered by B.A. Kratky from the University of Hawaii.

In essence, Kratky can be seen as the Deep Water Culture, but without a pump.


Deep Water Culture is one of the easiest Hydroponic systems to run, but Kratky makes it easier and excitingly cheaper. That is because, with Kratky, growers don't need to buy the electronic devices and the electricity to run it.
People say you can build a Kratky system and "set it and forget it". Plants are let to do their own things until harvest time. That's somewhat true. It is because Kratky is a completely passive system. There is no electricity used as well as no pumps and wick needed.  

Growers also don't have to change nutrients in the reservoir much often like other systems. 

So theoretically, Krafty is a low-maintenance system that can work on its own for weeks. 

How does it work?

The Kratky method

As you may have known what plants need from our nutrient post
Basically, plants require oxygen, moister, and lighting to survive. To reach its full potential growth, they will need macronutrients and micronutrients. 
The Kratky method supplies plants with all of these in a simple way: 

Nutrients are added to the container/reservoir. 

Plants are placed into a net pot with the growing media (like hydroton, rockwool,...) held by a lid, and hung above the water. 

Plants roots are partly submerged into the water and partly exposed to the air. This is to ensure that plants can get moister as well as oxygen.

As the plants grow, the water level will decline as plants absorb the water in the system, leaving a gap of the roots exposing to the air. The "air gap" is very important because it is where the plants respire. 

So that means towards times, plants are still able to take up sufficient nutrient, water, and oxygen.

For fast-growing vegs, when the water in the system is almost empty, your plants may have reached its harvest time. If you want to let the plant continue growing, you can add more water and nutrient solution, and recheck the pH level. 

Tools Needed

  • A container. Depending on how large the plants and how big you want your Kratky system to be. A milk jar also works if the plants grown are small.  
  • A lid. A plastic one or even a styrofoam also work. The lid is very important. It keeps plants from pests and disease, prevents water in the container from vaporing. And most importantly, it supports the plants above the water. 
  • Net pots. Again, choose the size you want. 
  • Growing medium. We prefer Hydroton as it is easy to work with, pH neutral, and have good air aeration 
  • Hydroponic nutrient. We use General Hydroponics Nutrient package. 
  • pH measurement tools. a pH meter helps check the pH level of your system.
  • A pH control kit. You should occasionally use the pH kit to check if the pH level of your system is not too low or too high and needs adjusting. 

What types of plants can you grow with Kratky Method:

The Kratky works best with leafy greens, plants that enjoy a fast-growing rate. These include lettuces, spinaches, herbs. 
You can also grow larger plants like tomatoes or peppers, but you will need a larger container. And growing larger plants will need your more regular checking to ensure the water and nutrient level at 2-3 inches in order to give the roots access to the enough water and oxygen as well.

Potential Challenges and Downsides of the Kratky Method

Suitable for small plants

Namely the leafy green ones like lettuce, spinach. It's not efficient for fruits like tomatoes, peppers, cucumbers and other heavy large-space craving plants. 

Not built for larger systems

If you want to have an efficient hydroponic garden that can surprise your friends, and provide some foods for your family, Kratky system can do well. But if you want to grow it big, or produce food on a larger scale, a recirculating and electricity-run system is more practical.


Kratky is a passive system that runs quietly. That can be inviting for pests like mosquitos and others like crickets, spiders, grasshoppers. It's just a natural reaction, so be sure to expect and handle them.

Covering the container is important

This is why the lid plays a crucial part. It helps protect the system from outside factors like pests, rainwater, temperature. Many people like to grow outdoors for the full sunlights. Make sure that rain water does not enter the tank. Too much of it, and the water level of your system can increase, plants can get drown. Also, the pH level, ppm of your system changes subsequently. So get some sorts of protection like a roof above the system. But mostly if your plants grow well, they can absorb and keep most of the rainwater from entering. For heavy rains, better to bring your system inside. 

Take control of other factors

In reality, Krafty is not completely hands-off. There are lots of variables that you need to be aware of.

Using high-quality water, thoroughly mix the nutrient and keep the nutrient water's pH at an appropriate level for the initial set-up are very important. Otherwise, you need to check and adjust them regularly later. But it's still better that you occasionally check the pH level, the water level, ppm to ensure plants' optimal growth.

Temperature can also not be stable most of the time. So keep the system in the places where there is no rapid change of it. Have some ventilation methods in the hot summer weather.

Bottom Line

Even though you will need a pump and the electricity to run like in the Deep Water Culture, Kratky method proves that you can still grow plants well passively, especially leafy greens. 

The Kratky method is no doubt a simple and relaxing way to try with Hydroponics. If I was to recommend a simple easy-to-build system for beginners and kids, the Kratky system would be definitely one of them.

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