Last year, I built a solar powered, off-grid hydroponic system, that was meant to be used outside and provide a very solid setup.

I made a extensive post about it, you can read it here.

I’ve been really happy with it, so I switched my whole balcony front row (6 pots) to it, improved it and fixed some pain points I had last year.

Each pot holds about 10 liters of nutrient solution and 30 l of LECA when completely filled.

Even though they are very big in size (and can support very large plants), each pot had a weight of about 15 kg under normal conditions the last time I lifted it.

Problems and fixes

My first problem last year was the substrate itself.

I used lava rock, because I got it cheap from a store nearby, and is supposed to be a great hydro medium.
I found it to be too heavy, dusty, hard to clean after use, and too sharp on the edges, hurting the roots after each wind or moving of the pot.

I now changed the substrate to LECA (hydroton/ expanded clay pebbles), which I found very inexpensive online, and doesn’t have the cons I listed. It’s very airy/ lightweight, has smooth edges, doesn’t hurt as much when you step on it (a feeling worse than stepping on a LEGO brick!) and wicks water better than lava.

I also improved the air flow by using net cups for ponds. Sadly, I already noticed them bending and one slipping through, so I had to melt the edges of the outer pots a bit, to create an edge that holds everything in place.

It will be way easier to lift them out now, since I attached some cords in the corners.

I also added a fine mesh and some wood floor tiles I had left over, which will prevent any debris (leaves, dead insects, cat hair, etc.) from flying into the reservoir and rotting.

The mesh is fixed to the inner pot by a velcro for easy removal.

I also added a filter sponge for the pump to prevent any clogs due to plant debris or rocks falling through.

Why this setup specifically?

Over the last year, I tried a few different setups. Kratky, DWC, etc., you name it.

I needed something robust for outdoor growing. I hate the idea of a single pump failure killing everything I worked for the last months.

So I made this setup, which is basically the same passive LECA hydroculture (semi-hydro) I use indoors too for my houseplants, but assisted with a weak USB pump that is powered by small individual solar panels.

This helps keeping the solution aerated and moving, but without the need for an air stone. The LECA has such a big surface area, that the gas exchange happens passively by diffusion.

It also prevents a salt crust from forming due to increased evaporation in summer. There’s still some evaporation, but that helps cooling the roots in summer heat. Besides that, it also assists in properly irrigating the plants when they are smaller and the roots can’t reach the nutrient solution.

Everything is modular, cheap and replaceable, and it can run without power for weeks theoretically.

The main reasons I built it, besides the pros I already mentioned, compared to other setups are:

1. I hate the constant noise that the air stones and pump made in my DWC setup last year, and this setup is almost completely silent.
2. It is hard to place trellises/ supports/ clips onto classic hydro setups. Here, we can just poke them into the LECA and everything is locked into place.
3. Many setups, like DWC, are too heavy for my balcony and use too much nutrient solution for my taste.

I will post more pictures once the plants I prepared are placed outdoors into the pots.

I’ve had it running now for a few weeks, to flush out the LECA and to see how it performs, just in case some major problem arises. For now, it looks very very promising.