DIY hydroponics - kratky and DWC bubbler


9 min read

If you want to try hydroponics here's a couple of easy, cheap and affordable concepts. Do it yourself hydroponic growing box for chilies!

We have two hydroponic growing methods, kratky and DWC (Deep Water Culture) bubbler. You can google either method for more detailed information. The difference is that kratky is just a passive box versus bubbler adds a little aquarium bubble pump to the bucket. Not much difference really. Both will work well!

Here's how I built my hydroponic growing box.

The first step was to find a box that does not let light through into the box. It needed to be sturdy plastic too. Lid needs to stay put steadily on the box. This one has handles on both sides that keep the lid firmly on place. The container size could be anything between 5L and 35L or even larger. The size will determine how often you need to top up water and nutrients. This box is approximately 30L and suited my needs perfectly.

Best part of this storage box is the wheels. I can push the heavy box back and forth easily because it rolls on wheels! 👍😁

A drill and round net pots can be handy. But really anything goes.

Drill a fitting hole to the lid of the planting box.

Here I am using weird shape net pot.

Measure twice cut once!

Here is the net pot fitted to the lid firmly.

I used some ziplock ties to make sure the cup does not come off.

The plant will be sitting in the cup and its roots will grow through these holes and reach water. Eventually the plant's roots will engulf the whole cup inside them.

Recycle reuse and so on they say, right?

This net pot is made from feta cheese container. Tasty and useful! 👍😁

Any cup with holes will do. You can buy the proper net cups online at amazon or aliexpress too. I didn't want to wait for the mail order so I ate the cheese instead. 😉

The lid of the box was white and allowed some light to get through.

I covered it with aluminium foil to block the sunlight. If light gets in there will be algae growth that can be a big problem for the plant's roots.

Foil will also reflect some extra light to the plant so it's a win win.

Making several is not much more labour than making one.

I always run out of space for plants!

Finally it was time to build a support frame for the plant. I bought support sticks from gardening store. They are really cheap, about a dollar each. I drilled snug holes to the lid and forced the support sticks through them. They sit in place quite firmly! Finally I bound the sticks together with metal wire at the top. The whole lid can be picked up by lifting it from the top of the frame. Sturdy! 👍

The lid, plant, cup and the support frame are all one sturdy unit. It can be lifted off for the duration of maintenance and cleaning with ease.

I had one hydroponic plant waiting in my other hydro unit. I pruned off about half of the foliage and some smaller roots.

The plant fitted perfectly in the net cup and the roots were large enough to reach the bottom of the bucket.

I was a bit worried that the plant might die because of the changes but it seemed happy the next day. Operation was a success!

I added water to the box until the water level reached the bottom of the net cup. About 1/4 of the roots are exposed to air and 3/4 are submerged in the water. This is important because the plant's roots will need oxygen from air.

Finally I added the hydroponic nutrients to water and measured the concentration of the solution with my EC meter, about 1000 ppm (some meters will show this as 1.0 but mine shows it in 1/1000 scale).

Kratky Method

The remaining space in the cup is filled with leca balls. The balls retain moisture for the roots and support the plant. The white cup is from the previous hydro growing unit. I could not remove it without harming the plant so I just allowed it to stay.

Cost of this whole mini project came to about 15 USD. The box was the most costly part.

Without any additional pumps or parts this is called a kratky method hydroponics according to its inventor's name. The setup is passive with no need or very little maintenance. Plant will draw nutrients and water from the bucket. It will deplete oxygen from the water. Water level will go down and the plant's roots will be exposed to air. This enables plant to draw oxygen from air instead of water. It is super simple and will work great if the box is kept clean and water changed sometimes.

Adding water and nutrients should be done periodically, perhaps when there is 1/3 of the water left. It is also good idea to clean up the bucket and refill it sometimes to prevent root rotting. Just don't fill the bucket all the way up because that will risk drowning the plant! Maybe about halfway is okay.

Upgrading to DWC Bubbler

If you add an aquarium pump with a porous bubble rock to the bottom of the kratky bucket this setup becomes a DWC "bubbler". It bubbles.

The bubbler modification aerates the water and reduces the risk of root rotting. Bubbler adds oxygen to water.I added water to the box until the water level reached the bottom of the net cup. Most of the roots can be in the water with the bubbler add-on. The water pump ensures adequate oxygen content in the water. More oxygen in the water is better!

Finally I added the hydroponic nutrients to water and measured the concentration of the solution with my EC meter, about 1000 ppm (some meters will show this as 1.0 but mine shows it in 1/1000 scale).

The chili plants can grow really large in this setup, even 2 meters or taller, depending on the size of the bucket!

Yields can be really good too.

Easy and fun build! 😛👋

A week later the plant is very healthy and grows a lot of new leaves. 👍

I also added a cheap aquarium pump to aerate the water. This makes the setup a DWC (Deep Water Culture) bubbler. There is an air tube and air rock at the bottom of the box.

The reason why I decided to add a bubbler was that apparently pepper and chili plants can grow faster with a bubbles in the water. This does not happen with all kinds of plants, but it will work with peppers. The exact reason why this happens is probably that bubbling mixes and disturbs the water surface and moisturises the roots within the bucket. There is just more moisture and nutrients available, perhaps it is that simple. The roots can grow larger and the plant gets bigger faster. Makes sense to me.

And here we go, a bunch of bubblers bubbling!

The plan is to block the view from neighbours using the chili plants.

But how efficient is the bubbler compared to kratky?

Picture here shows passive kratky (left) versus DWC bubbler (Right). The DWC bubbler is growing significantly better.

Reference to the above. The picture is from this video from "Growing answers":

Growth and Harvest in a DWC Bubbler

This is my largest DWC bubbler.

Two plants in 75L capacity tank.

Their trunk is 5cm thick at the age of 7 months, grown from seeds.

The first harvest yielded nearly one kilogram of peppers.

Harvests happen every 3 months or so, possibly allowing total of 4 kg of super hot peppers annually per one DWC setup.

Here's an example how to cover the roots with leca clay balls. You can get plastic net from gardening store that keeps the balls from falling down through the roots to the bubbler.

If you live in a country with mosquito problems like I do, the net and clay balls will also prevent mozzie problems. Remember, you might need to also put anti-mozzie detergent to the water if your area has real problems with the mosquitoes.

Big plants can be decorative, especially in the christmas time!

No need for a christmas tree!

Growing from Seed to Sapling

Here's a fun way to germinate seeds and grow saplings to a bit larger size before moving them to large DWC bubbler container.

I started with a small one litre kratky bucket. This one is an used bulla ice cream container.

I used a net growing cup / pot to draw the approximate size for the hole and cut it out with scissors.

The net pot fits like a glove!

Seeds are just gently plugged inside the rock wool. Make a tiny hole and plug them in!

Imagination is your limit! Here we have four seedlings starting. They will all go eventually to grow boxes when they grow a little larger. Note that the rock wool cubes need to touch the surface of the water to keep moist.

For the time being they will grow in these mini kratkys that I tinkered for them from old food containers. You could just as well keep them in one big germination vat too. Whichever way works for you! Give them light and mild fertiliser liquid so that they grow!

Here's another idea for growing the seedlings a bit larger. Why not use a plastic shelf container box from IKEA?

I just drilled holes for net cups on the lid. Perfect for growing them before switching to a larger container.

The sapling looks healthy.

Finally I added hydroponic growing solution to the container. About the same strength I use for mature plants. Roots are about half submerged to the water.

The plant will soon start growing aerial roots. They provide oxygen for the plant. The aerial roots look fluffy and delicate. The water level should remain below these aerial roots so that plant can get oxygen.

He moved to my old protein powder keg! That should keep him going for a good while.

I found some algae growth in the water after a couple of weeks. This is why the keg needed to be covered with tinfoil. Painting it black would have worked too but I didn't want the water to be too warm because sunlight would heat the black surface. Tinfoil is better.

Here's cherry bomb chilies growing in the same kratky. Nice!

Kratky power!

// Chilious