I want to present you my setup I "invented" myself. You can imagine it as a recirculating drip system, but mixed in with semi-hydroponics and a wick setup. And all of that completely "passive"!

How it started

Initially, I wanted a completely passive wick system. I'm a really big fan of passive hydroponics, e.g. the Kratky method or LECA (semi-hydro). While I also like DWC systems and all those others too, they almost always need access to the power grid.

So, I built my wick system myself and transplanted one of my plants from a DWC system into the passive wick system.

By doing that, I damaged quite a lot of roots, and that, in combination with lots of debris from the environment (seeds, leaves, etc.), and stagnant water, caused anaerobic conditions. It smelled horrible, and the plants looked very sad!

Adding peroxide daily and changing the water every few days didn't help. I had 3 identical systems, and all of them behaved the same.

There had to be some kind of oxygenation!

When I was able to flush it all out somehow, everything worked again as it should be after a few weeks. There was no more smell, the pH stabilized, and everything was fine.

Then, one more problem showed: the wick wasn't strong enough. When it was hot outside, especially my hemp plant (lots of surface area, high water demand) looked very thirsty.

It was also hard to adjust the solution, the whole system was very inflexible.

So, I had to make an upgrade!

The current setup

My current drip system is almost the same as the wick system before, but with an added water pump and drippers. You can see the schematics in a second.

How it works

When it's sunny (and hot!), the plant needs way more water. Gladly, we have our solar panel. As soon as the sun comes out, the pump turns on and feeds the plant.

And when it's really hot, the big surface area of the substrate below cools down the roots by evaporation, so they are always optimally saturated with oxygen.

Because the nutrient solution is constantly moving, it doesn't need to be additionally oxygenated with an air pump. The LECA or lava stone is so porous, that it traps just enough oxygen, and the high surface area allows beneficial bacteria and fungi to settle. If any organic debris falls in (insects, pollen, leafes, etc.), it just gets eaten by the microorganisms. I changed the nutrient solution rarely, and it always worked fine.

In the night, or cloudy days, the pump is off. Then the plant feeds itself from the moist clay balls or the wick below.

And, when it's rainy, the rain washes off all salts from the minor crust that has built up.

What's also cool is that you can just remove the plug from the end of the tube and then flush the reservoir or take a sample to check the EC and pH.

Schematics

1. Outer container, holding the nutrient solution
2. Inner container, holding the substrate and the plant
3. The Wick, drawing up water and filtering it
4. The substrate (LECA or lava rock)
5. USB-powered fountain pump
6. Solar panel with USB ports
7. Tube with holes or drippers
8. Optional: a water level indicator and some cover plate against direct sunlight

How to build it

• You need a big plant pot as the outside container, and a smaller one that fits right in.
  I got mine from a local nursery, the pots are literally everywhere!
• Now, you drill or burn some holes into the inner pot. I recommend adding them not directly on the bottom, but a few fingers spaced above. That way, the nutrient solution can form a small puddle, that feeds the plant and keeps the substrate moist, even when there isn't any sun for a few days. I did both and both worked fine.
• Now, add a wick. I used a kitchen towel made out of polyester. Don't use cotton! Any organic material will rot in a few days!
• Then, fill it up with your substrate. Lava rock is cheaper and gives the plant more stability, but is very hard to wash off and can damage the roots. LECA became more of my choice, as it is very easy to clean, is more lightweight, and draws up moisture better, but is also more expensive and provides less stability.
• Add the pump to the reservoir, and make your dripping tube. I bought special sprinkler-drippers, but you can also just pierce some holes into the tube. I did that in the beginning too, and it worked fine. The pump is a cheap one (7€) from Amazon/ Pet supply store, and the sprinklers are bought dirt cheap.
• Add some cover to the surface. I didn't notice much algae build up, but even if those aren't a problem, too much direct sunlight might evaporate too much moisture, and leaves fall onto the substrate.
• Finally, plug in your pump into the solar panels. The solar panel is bought from Amazon, and is pretty inexpensive. Make sure it is water resistant! Ideally, the maximum power generated should be double of the pump.

I don't recommend buying a pre-made solution with the combination of pump and solar panel. I already saw quite a few of them in my garden center, but they are absolutely not modular. If one part breaks, you have to replace the whole combination.

In total, the setup is pretty cheap, at least for home use. I used it for this grow season and I already bought parts for a few more next year!

Pros and cons, compared to other systems

Pros

• Doesn't require "sterile" conditions, not as much as other systems.
• Absolutely great for bigger plants, e.g. tomatoes, cannabis, peppers, etc., as the substrate gives a lot of stability for the roots.
• Doesn't require electricity/ power from outside.
• Very reliable. Even, if the pump or anything else breaks, it won't end in a total disaster.
• Silent. Almost all systems that use an air stone or spray nozzle generate a lot of noise, this one doesn't.
• Easy sample taking. Just grab a jar, remove the plug from the tube, fill up the jar, measure your EC and pH, and done. No need to disturb the roots or lift a lid.
• Lightweight. You only need enough water for the pump to cover, and the LECA isn't dense.

Cons

• You need to clean a lot of LECA in the beginning.
• Slightly higher starting costs. Hydroton is expensive, and you need the pots, pump and solar panel. But, it's also not much more expensive than other systems.
• If you have a slug infestation, like I had, it is horrible! The moist clay pebbles are the perfect home for any snail. If they die, they leave a lot of biomass and dirt.
• Hard to check the water level and root health. In my DWC, I just lift the lid a few cm, here it's harder. You'll notice when the nutrient solution is empty, because then the pump will run dry, and it becomes loud, but the water level indicator is a thing that I will definitely add next year.