Kratky Hydroponics (Kratky Technique: What You Need To Know)

Kratky hydroponics is one of the simplest and most popular methods of passive hydroponics. These systems require no electricity and little maintenance to yield beautiful crops at home!

Kratky hydroponics is a passive hydroponic method where growing plants are suspended above a reservoir of nutrient-rich water. This may sound intimidating but it is incredibly simple and rewarding. In this article, we will go over everything you need to know about Kratky hydroponic systems and how you can assemble your own DIY system at home!

Let’s get started!

What Is Kratky Hydroponics?

Growing plants hydroponically means to grow plants without using soil. In traditional gardening, plants are grown in soil which is simply a source of nutrients to fuel their growth.

Hydroponics is one method of growing plants without soil.

In hydroponics, soil is replaced with a nutrient solution that is added to the water that the plants are grown in. Through the process of hydroponics, nutrients are always surrounding the roots of the plant resulting in fast growth rates and plentiful harvests.

If you are looking for a foolproof, soil-free microgreens growing kit, try out The Good Box (you can learn more here!)

But, that is only skimming the surface of how hydroponics work and why they are so efficient. There are many different hydroponic techniques, one of the most popular being the Kratky technique.

Kratky hydroponics is a passive hydroponic method where growing plants are suspended above a reservoir of nutrient-rich water. The method is named after Bernard Kratky, a researcher at the University of Hawaii who discovered the technique himself.

kratky hydroponics
In Kratky hydroponics, plants are suspended above a reservoir of water with all the nutrients they need.

The motivation behind designing the Kratky system was to discover how to grow plants hydroponically without the need for pumps. The Kratky technique is a perfect example of how to work smarter and not harder! 

Today, the technique is arguably the simplest of all hydroponic systems requiring no electricity and just a few materials to assemble. The Kratky hydroponic method is utilized by home gardeners and hobbyists and throughout large scale agriculture. 

The Kratky hydroponic method is one of the most popular methods of passive hydroponics for its notable advantages:

  • Because no electricity is needed, the Kratky method is utilized in remote places to grow fresh produce fast. Additionally, there is no risk of losing your crops to power outages which is often a concern with other hydroponic gardens that require electricity.
  • The Kratky hydroponic method is ideal for people who simply want to assemble the system and let it do its thing. You just have to remember to check the nutrient water levels from time to time and refill as needed.
  • The Kratky method requires no pumps, timers, or filters making it not only budget-friendly to assemble but extremely easy as well. 
kratky hydroponics
The Kratky hydroponics method does not need any pumps, timers, or filters.
Image courtesy of user:
Luxvix55 via:
Wikimedia Commons https://commons.

Despite the simplicity of this system, there are a few disadvantages to be aware of:

  • The reservoir of stagnant water can attract pests if left uncovered. You do not want flies and other bugs to find their way into your system so it is important to keep it covered!
  • Many plants require a specific water temperature in order to thrive which can be more difficult to maintain in a Kratky hydroponic system. 
  • Because the Kratky system does not use electricity to maintain itself, it is easier for surrounding elements to fluctuate growing conditions. Because of this, it is best to keep Kratky systems indoors where they are less susceptible to changes in temperature and weather. 

How Does A Kratky Hydroponics System Work?

A Kratky hydroponic system is a passive form of hydroponics meaning that water circulation is not necessary. In fact, a Kratky hydroponic system does not require electricity at all.

How it works is that the roots of a plant are submerged in nutrient-dense water while the upper plant sits in a raft that remains above water. The water itself remains completely stagnant throughout the entire growth process. As the plant gets bigger, more water is absorbed revealing more of the roots to oxygen. Once the water runs out, the plant is ready for harvest. 

There are two types of hydroponics: passive and active. Kratky hydroponic systems are a passive form of hydroponics.

kratky hydroponics
The plants in a Kratky hydroponics system are suspended above the water by a raft.
Image courtesy of user:
Luxvix55 via:
Wikimedia Commons https://commons.

Passive hydroponics simply keeps the plants sitting in still water as they grow. Active hydroponic systems use pumps to cycle water throughout the system and to the plants.

There are different ways in which you can grow plants hydroponically. Many hydroponic methods are similar to one another.

The Kratky hydroponic system is similar to the “deep sea culture” hydroponic system. But, the two methods are still different in their procedures.

The Kratky method is passive while the deep sea culture method is active (it requires an air pump). Yet, both methods include suspending roots into reservoirs of nutrient-dense water.

What Do I Need For Kratky Hydroponics?

Putting together a Kratky hydroponic system is a super simple and fun DIY project requiring just a few items:

  • A simple DIY Kratky system can be made using a mason jar. But, committed growers often use 5-gallon containers.
  • In a mason jar Kratky system, the lid is already perfect. Having a lid/cover is essential to prevent any of the water from evaporating out of the system. 
  • Net pots are little pots with holes so that the plant can be securely held while the roots can still grow downward into the water reservoir. The holes at the bottom also allow for proper drainage preventing root rot.
  • A growing medium is necessary to support the plant once it starts to root a hemp grow mat or coco coir mat works great.
  • Do your research to find the nutrient solution that is best for your plants of choice.
mason jars
A mason jar will work for a small Kratky hydroponics system…
5 gallon bucket
but a 5-gallon bucket will hold a lot more water, and leaves space for a lot more root growth.

This step-by-step tutorial is one we particularly love for assembling a simple yet effective Kratky hydroponic system using an empty yogurt container. You’ll have your own mini garden in no time!

How Often Do You Change Water In The Kratky Method?

The Kratky method is a passive form of hydroponics meaning that the water remains stagnant throughout the entirety of a growing cycle. Therefore, there is no need to change the water during a growing period.

When executed perfectly, the plant will be ready for harvest once there is no more water in the system. But if that is not the case, continue to add water until your plant is fully grown.

You won’t need to change the water in a Kratky hydroponics system, but you might want to add more if the reservoir gets low before the plant is done growing.

To start another crop once the plant has been harvested, the water tank can be refilled and new plants can be placed on rafts atop the tank. It is important to remember to clean the system thoroughly between every three to five growing cycles.

Do You Need An Air Pump For Kratky Hydroponics?

Kratky hydroponics do not require an air pump! In this passive hydroponic method, the roots of the plant are submerged into a reservoir of nutrient water.

kratky hydroponics
You do not need an air pump for Kratky hydroponics, since the roots are in a reservoir with nutrient-rich water.
Image courtesy of user:
lienyuan lee via:
Wikimedia Commons https://commons.

As the plant takes in nutrient water, water levels go down, and the roots grow longer. As the plant grows more mature, more of the root becomes exposed to oxygen.

Oxygen is always accessible to the plant in the Kratky method therefore an air pump is not necessary.

What Can You Grow With The Kratky Method?

Different plants have varying growth rates and nutritional demands, therefore it is best to grow a mono-crop (single variety of plant) in each container. If you grow different plants in the same container, the plant with the fastest growth rate will absorb the most water, leaving the slower-growing plants to die. 

Leafy greens and herbs are the best plants to grow in a Kratky hydroponic system. Leafy greens and herbs are small, lightweight plants that grow fast!

hydroponic lettuce large scale
Greens like lettuce or spinach (or herbs) are great for growing in a Kratky hydroponics system.

Lettuce, spinach, bok choy, kale, romaine, basil, and celery will thrive in Kratky hydroponic systems. They will be ready to harvest in just a few weeks. 

Plants that require larger quantities of water are not ideal for Kratky systems. For example, tomato plants are known for being exceptionally thirsty and would not do well in the limited, stagnant water of a Kratky system.

ripe tomatoes on vine
Tomatoes need lots of water, and they might be easier to grow with traditional gardening (in soil) rather than in a Kratky hydroponics system.

Active hydroponic systems with pumps and recurring watering cycles are best for fruiting plants. 

Can You Grow Strawberries In A Kratky Hydroponic System?

You can grow strawberries in a Kratky hydroponic system with patience and a bit more maintenance. Young strawberry plants can be placed into a Kratky hydroponic system and begin to produce fruits in as little as one month’s time!

Although it is an option, it would take much longer to grow the strawberry plants from a seed. Therefore, we recommend starting the process with young plants with already established root systems. 

hydroponic strawberries
You can grow strawberries in a Kratky hydroponics system. However, the plants can be picky about their environment, so watch temperature fluctuations and light levels.

Compared to other types of plants, strawberry plants tend to be pickier about their environment in hydroponic systems. It is important to remember to keep their water between 60 and 70 degrees Fahrenheit at all times.

Strawberry plants also require 14 to 16 hours of light each day. Therefore, it is essential to grow your strawberry plants in an area with plenty of sun or beneath artificial lights. 

In roughly 8-10 weeks time, you should be able to harvest red strawberries from your Kratky hydroponic system! 


A DIY Kratky hydroponic system is a perfect first project for first-time hydroponic gardeners because it requires just a few basic items and little maintenance. Keep it simple with the Kratky technique!

You might also like to try NFT hydroponics, an alternative to the Kratky technique.

DWC hydroponics is another alternative method you might want to read up on.

If you want to try out a hydroponic tower, you can learn more about them here.

If you want to learn how to grow microgreens hydroponically, you can learn more here.

You can learn about all different types of plants you can grow hydroponically here.

You can learn about aquaponics (and how it compares to hydroponics) here.

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About the author:
Sofi is a passionate writer who studied communications and environmental studies at Eckerd College. You can get in touch with Sofi at

Sofi L.

Jon M

Hi, I'm Jon. Let's solve your gardening problems, spend more time growing, and get the best harvest every year!

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