What Is Kratky Hydroponics? (FULLY EXPLAINED)

You’ve probably heard terms like hydroponics, aquaponics, maybe even aeroponics or semi-hydroponics if you’re interested in alternative growing methods. There are numerous ways to grow plants successfully without the mess and stress that comes with soil, including Kratky hydroponics.

This form of hydroponics is by far the most simple to learn and master (ANYONE can do it) of all “advanced” and “soil-less” gardening methods. Even more? It requires ZERO electrical components like water pumps, filters, or air stones (unlike almost ALL other forms of soil-less growing).

That means it is by far the most AFFORDABLE form of hydroponics there is. Do we have your attention yet? If so, read on below to discover exactly how super easy no-soil gardening is with Kratky hydroponics!

What is Kratky Hydroponics?

Kratky hydroponics is a simple method for growing plants without the use of soil, traditional labor-intensive gardening techniques, or the typical components found in hydroponic growing systems. This super easy to use form of hydroponics consists of a reservoir filled with water and nutrients, a lid or cover, and a net pot or similar anchor for plants.

How Exactly Does a Kratky Hydroponic System Work?

The Kratky technique of hydroponics revolves around simple gardening know-how and low-level hydroponics; plants need water, air, sunlight, and nutrients, all of which are attainable easily attainable without the use of electronics, hoses, pumps, or other gadgets (like most hydroponic and other soil-less growing methods include).

With Kratky hydroponics, a simple container is turned into a reservoir for water and liquid nutrients. The top of the container holds either a lid or growing bed (which are more or less interchangeable/the same thing).

Plants are anchored into the top of the reservoir’s lid in net pots, Rockwool, or some other sort of inert medium (for the most part). Some Kratky systems may include pots with soil, peat moss, or other organic mediums as well (but these are typically exceptions to the rule).

The roots of the plants anchored to the top of the system hang down into the water and nutrient solution, wicking up all the moisture and food they need. The tops of the plants are exposed to the sun, or artificial lights (as you see fit).

How Does Kratky Hydroponics Differ from DWC Hydroponics?

If you’re familiar with hydroponics, in general, you’re probably wondering why the system isn’t qualified as deep water culture (DWC) hydroponics.

The answer lies in the most simple aspect involved with the Kratky method: a thin layer of air is purposefully left between the surface of the water in the reservoir and the bottom of the lid/top of the system.

It is from this small inch or so tall space that the plants absorb fresh oxygen through their roots. There is no air hose, air stone, water pump, or moving components in the Kratky system, unlike in DWC systems.

DWC hydroponics are similar to Kratky systems, except for a couple of key differences: they include at the very least an air pump, hose, and air stone to oxygenate the water and feed air to the plant’s roots, and they tend to include much deeper reservoirs.

How to Build a Kratky Hydroponic Grow System

Building a DIY Kratky hydroponics system is genuinely an easy process; take a container, modify the lid to hold a net cup or piece of Rockwool, add water and nutrients, and you’re ready to grow something!

Below, we describe how to build your own Kratky growing system step-by-step in just a few minutes.

Supplies

Before you get started, there are a few supplies that you’ll need to gather:

• Container with a lid (a shallow tote or small bucket works best)
• A netted pot (you can even make one yourself if you prefer)
• Clean fresh water (if using tap water, make sure it is “soft”)
• Liquid nutrients (varies depending what plant/crop you will grow)
• Optional supplies: foam (rather than a lid), Rockwool or peat pellets (rather than a netted pot)

You also need some sort of sharp tool like a knife or razor.

1. Clean and Sterilize EVERYTHING

The first step to building your own Kratky Hydroponics system is cleaning and sterilizing EVERYTHING. From your knife to your container and netted pot, clean it all with hot soapy water before moving forward with putting together your system.

If you’re building a Kratky from scratch, with spare parts (like we did), you may need a bit more time for this step.

But, even if you bought your parts brand new from the store, you still need to wash them and rinse them to remove any harmful residue that might contaminate your system.

2. Modify Your Lid to Fit a Netted Pot

Use an Exacto knife, snips, or some other sharp tool, cut a circle out of your lid. The best way to measure for the circle before you cut is to flip your netted pot upside down and trace it around it with a marker.

Take your time on this step, as it is crucial that your lid fits correctly, holds the plant properly, and blocks excessive light from reaching the water. Measure twice, cut once!

3. Turn Your Container into a Reservoir with a Lid

Once you’ve cut a hole into your lid and made sure your pot fits it, it’s time to test the seal. A tight seal is crucial especially if you’re going to sit your system outdoors (as it prevents evaporation).

Our lid was a perfect fit, because it actually came with the container, to begin with. If you’re working with foam, measure twice and cut once!

Also, don’t worry about a seal, in the case you’re working with foam. Just make sure it sits flush all around the lip of the reservoir.

4. Prepare (or Create) Your Netted Pot

If you haven’t already purchased or created one, now is the time to prepare your netted pot. It can be made out of a yogurt cup, a starter pot, a hydroponic net cup, or even a plastic water bottle.

Whatever you use for your netted pot, just remember that it needs to allow roots enough room to get through to the water as well as to anchor themselves in the pot.

5. Add Water and Nutrients

Once all of your parts are cleaned, sterilized, and modified, you’re ready to fill your reservoir up with water and nutrients.

This can be done in several ways. We suggest mixing nutrients in a bottle of water, pouring them in, and topping the rest of the reservoir off with fresh water (remember to leave an inch or so of space between the top of the bucket/lid and the surface of the water).

Keep in mind that the best type of nutrients to use in any hydroponic system varies from plant to plant. This PowerPoint Presentation about How to Choose the Right Fertilizer for Hydroponics, from Purdue University, is a great resource and discusses the subject in great detail (pay close attention to pages 14, 15, and 16!).

If you have a meter handy, double-check the pH level of your reservoir once you’ve filled it up. The pH should be roughly between 5.5 and 6.0, with an EC or around 1.

6. Put the Lid on and Prepare Your Plant

Now that your reservoir is filled with water and nutrients, fit your lid onto the top and double-check things.

The picture above shows the petted pot in place, but you should wait until the next step before placing it into the lid.

Also, make sure that there is enough space between the bottom of the lid and the top of the water level for your plant’s roots to breathe.

If everything else has checked out, move on to preparing the actual plant you’ll be growing in your Kratky hydroponics system.

This is possible in a number of ways, we suggest simply lifting it out of its starter pot and removing soil by hand.

Once the majority of the soil is clean, finish off the job by rinsing the rest with cool water.

When your plant is cleaned down to the roots, carefully insert a few of the roots through the bottom of the netted pot, and a couple through the sides if possible. This helps to anchor the plant.

You can also opt to add in a growing medium like LECA or pebbled for extra anchoring.

7. Insert the Netted Pot and Plant

With your plant safely anchored into the netted pot, insert it into the hole in the lid of your reservoir. After a couple of seconds, lift it back up and check the bottom.

If the bottom of the netted pot and the plant roots are dripping water, you’re good to go. If not, you’ll need to add a bit more clean fresh water.

Again, make sure to leave at least an inch or so of space between the lid and the water, that way the plant can breathe.

8. Place the System Outside or Under a Light

Now that all the “hard work” is over, it’s time to sit your Kratky hydroponics system outside or under a light and leave it to work its magic.

If you’ve done a good job, and added enough nutrients, your plant should recover from transplant shock in as little as a few days, or in as much as a couple of weeks (depending on size and species).

At this point, all you have to do is keep the water topped off, check the pH regularly, adjust as needed, and keep the pests away!

Suggested Reading: INDOOR SEMI-HYDROPONICS: HOW TO GUIDE (WITH PICS)