Hydro tower, NFT, Kratky or DWC: which system suits you?
All common soilless systems fairly explained: how they work, what equipment they need, how much space and care they take and which plants they suit. With a comparison table and my own experience.
What all systems have in common
In every hydroponic system the plants grow without soil. The roots get water and nutrients directly from a nutrient solution. They also need oxygen, and this is exactly where the systems differ: sometimes the water trickles over the roots, sometimes it flows as a thin film, sometimes the roots hang in water and an air stone brings air, and sometimes the water level simply drops slowly.
What stays the same everywhere: you do not water, you measure. The EC value shows you how much fertiliser is in the water, the pH valuewhether the plant can actually take up the nutrients. You will find the basics in my overview of Hydroponics.
1The hydro tower
My system for windowsill, balcony and garden.
In a hydro tower the plants stand one above the other in vertically stacked segments. A small pump carries the nutrient solution from the container to the top. From there it trickles down through the segments, wetting the roots on the way. The solution runs in a loop and is used again and again.
The pump does not have to run all the time. Indoors I set 5 minutes on and 30 minutes off, outdoors in great heat 15 on and 15 off. During the breaks air gets to the roots. The big advantage: very many plants grow on a small footprint, because the tower goes upwards.
| Tower | Well suited for |
|---|---|
| narrow vertical tower | lettuce, herbs, pak choi, kohlrabi, peppers with a frame |
| wide tomato tower HydroFlex Tower Largo Uno | tomatoes, cucumbers, peas |
Some manufacturers also call vertical towers aeroponics. Strictly speaking that is not quite right: in the tower the nutrient solution trickles over the roots; it is not misted through nozzles. I show you how to build a tower yourself in the guide Build a hydro tower. And you can read how it hangs securely on a wall or fence under hydro tower wall mounting.
2NFT: the channel system
Nutrient Film Technique, made for lettuce and herbs.
In an NFT system the roots lie in flat channels with a slight slope, about 1 to 3 cm per metre. A pump sends a thin film of nutrient solution through them. The roots do not stand in water, just a little in it. That way they get nutrient solution at the bottom and air at the top. At the end of the channel the solution runs back into the tank.
NFT is very widespread in commercial lettuce growing, because it is easy to expand and saves water. The catch: the film is only a few millimetres high, and there is hardly any reserve. If the pump fails or a hose clogs, the plants wilt quickly in warm weather. That is why the pump classically runs without a break. Large plants with strong roots clog the channels, so NFT is mainly for lettuce, herbs and leafy greens.
Everything about slope, flow rate and values can be found on the page about the Nutrient Film Technique (NFT).
3Kratky: no technology at all
No pump, no air stone, no electricity.
The Kratky method is the simplest system of all. It was developed by Bernard Kratky at the University of Hawaii. The plant sits in a net pot in the lid of a container, and the roots reach into the nutrient solution. That is all it takes.
The trick: the plant slowly drinks down the water level. A moist air space forms between the water and the lid. The lower roots take up water and nutrients, the upper ones get oxygen from the air. That is why you do not top up to the brim with Kratky, otherwise the air roots are under water again. Better plan the container big enough from the start for the first fill to last until harvest. For lettuce that is about 3 to 5 litres.
I explain it step by step on the page about the Kratky method.
4DWC: roots in water, air from the air stone
Deep Water Culture.
With DWC the roots hang permanently in the nutrient solution, just as with Kratky. The difference: an air stone constantly brings oxygen into the water. That is why the water level can stay high here, and you top up normally. The air stone runs continuously, day and night, because roots breathe around the clock. It goes straight into the socket, not on the timer.
I use the DWC principle every day: in my propagation station the roots hang in standing water, and in the HydroFlex Tower Largo Uno for tomatoes too. In both, the air stone always runs. The warmer the water, the less oxygen it can hold. From about 25 °C it gets tight for the roots without an air stone.
| Kratky | DWC | |
|---|---|---|
| Roots | in the nutrient solution, at the top in the air space | permanently in the nutrient solution |
| Air pump | none | continuously, day and night |
| Electricity | no | yes, for the air stone |
| Water level | drops, do not top up to the brim | stays high, top up normally |
| For me | for trying out with lettuce | propagation station, tomato tower Largo Uno |
HydroFlex Tower for indoors and outdoors, seedling box, seedling station, support rings and my own nutrient. After you buy, I’ll help you on WhatsApp.
To the shop ›Two more systems: ebb and flow and aeroponics
Ebb and flow
Here the plants stand in pots or substrate in a tray. A pump floods the tray with nutrient solution at intervals. An overflow determines how high the water rises. Then the solution runs back into the tank, and fresh air reaches the roots. The system is flexible and suits many types of plant, for hobby growers as well as in the greenhouse.
Aeroponics
In aeroponics the roots hang freely in a closed chamber. Fine nozzles spray them regularly with nutrient solution; whatever drips off is collected and reused. The roots get a lot of air this way. But the technology is demanding: the fine nozzles can clog, and because there is no reserve at the roots, a pump or power failure quickly does damage. Aeroponics is more something for tech enthusiasts.
All systems compared
| System | Pump | Air pump | Space | Effort | In a power cut | Well suited for |
|---|---|---|---|---|---|---|
| hydro tower | yes, at intervals | useful, a must outdoors from 25 °C | little floor space, goes upwards | medium | roots stay moist for a while | lettuce, herbs, pak choi, kohlrabi, peppers |
| NFT | yes, usually continuously | not needed | a lot of space in width | medium to high | critical, hardly any reserve | Lettuce, herbs, leafy greens |
| Kratky | no | no | flexible | very low | no problem, no electricity needed | lettuce, herbs |
| DWC | no | yes, continuously | flexible | low | roots stand in water, briefly no problem | lettuce, herbs, and tomatoes in the tomato tower |
| Ebb and flow | yes, at intervals | no | tray with tank | medium | substrate holds some moisture | many plant types |
| Aeroponics | yes, with nozzles | no | compact | high | very critical | for tech enthusiasts |
There is no single best system for everyone. Each has its strengths. What matters is what suits your space, your daily routine and your plants.
How to find your system
| Ask yourself | Then this suits you |
|---|---|
| Little floor space, but room upwards? | hydro tower, also on the wall |
| Just want to try it out, at almost no cost? | Kratky with one lettuce |
| Lots of lettuce in rows, room in width? | NFT |
| Large, thirsty plants such as tomatoes? | DWC, for example in the tomato tower Largo Uno |
| Hardly any time for care? | Kratky or a tower with a large container |
| Enjoy technology and tinkering? | aeroponics or a self-built NFT |
An honest look at budget and care is worthwhile: Kratky costs almost nothing. Tower and NFT need a pump, timer and a bit more material, but many more plants grow at once. The more technology, the more can fail. A spare pump is therefore always part of pump systems.
Build it yourself or buy ready-made?
Building it yourself is usually cheaper, and you can adapt everything to your space. But you need some practical skill and time. A ready-made system is ready to use immediately and all parts fit together. For beginners that is often more relaxed, but it costs more.
A few years ago I started myself with bent sewage pipes on the house wall, planted with strawberries. I would not do it that way today. Today I 3D print my HydroFlex Towers myself from UV-resistant PETG. They are modular, can be extended or shortened and so fit on the windowsill just as well as in the garden.
My tips for your start
- Start with lettuce and herbs. They grow fast, need little space and little fertiliser.
- Start small and expand step by step once you have gained experience.
- Measure regularly, always EC first, then pH. My pH target is 5.8.
- In a running system top up with ready-mixed nutrient solution instead of plain water.
- Keep the container and lid light-tight and clean, then algae have no chance.
- Make sure there is enough light and some air movement, indoors with a lamp and a small fan.
- Look at your plants regularly. You spot pests and deficiencies best early on.
- Write down your values. Then you quickly see when something goes off track.
When the water needs to be changed completely and how to do it without lugging, you can read in the article Water changes in the plant tower.
Equipment you need for a tower
Small submersible pump 8 WQuiet submersible pump that brings the water up in the tower. Best to get a spare straight away.17,99 EURView on Amazon*To Amazon*
Interval timer with cycle functionWith it my pump runs for 5 minutes and then pauses for 30 minutes, day and night.14,99 EURView on Amazon*To Amazon*
AquaForte Hi-Flow V-30 air pumpAir pump for the air stone that brings oxygen into the nutrient solution. Essential for DWC.51,94 EURView on Amazon*To Amazon*
Mars Hydro VG80 LED grow light 120 cmLong LED lamp for indoors when the light at the window is not enough.79,99 EURView on Amazon*To Amazon** Affiliate link: if you buy through it, I earn a small commission. Your price stays the same. Prices incl. VAT, as of 9.11.2026.
* Affiliate links (Amazon): if you buy, I receive a commission; your price stays the same.
Frequently asked questions about hydroponic systems
Which hydroponic system is the simplest?
How does the Kratky method work?
Can I top up the water to the brim with Kratky?
What is the difference between Kratky and DWC?
What does DWC stand for?
How long does the air stone run with DWC?
Where does Frank use the DWC principle himself?
What does NFT mean?
What slope does an NFT channel need?
What happens with NFT if the pump fails?
Which plants is NFT suitable for?
How does a hydro tower work?
How long does the pump run in the hydro tower indoors?
Which plants fit in the narrow vertical tower?
Why do tomatoes not belong in the vertical tower?
How does an ebb and flow system work?
How does aeroponics work?
What is the disadvantage of aeroponics?
Is a hydro tower aeroponics?
Which system needs the least floor space?
Which system is most robust in a power cut?
What do I top up a running loop system with?
Which pH value suits most plants in hydroponics?
Which plants should I start with as a beginner?
Build a hydro tower yourself or buy one?
More on the individual systems: Build a hydro tower, hydro tower wall mounting, NFT, Kratky method and DWC and the overview of Hydroponics.
Continue with your own growing
168 pages, simply explained for beginners and with videos on the topics (in German). Exactly how I grow myself: from sowing to harvest.
More about the book ›A few questions about space, location and what you want to harvest, and you get a recommendation.
To the tower advisor ›Questions about your setup? Message me on WhatsApp.
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