Rack-mount hydroponics

You did mention the reason for a server rack as a matter of circumstance. But if I were to do and really want the Hydropnics part, I’d sell the Server Rack (good price) and buy the cheaper Pallet Racks. The first thing that comes to mind is that it will be easier to plan, pluck, change lights, etc.

Server Racks - you don’t interact with them often, but you will need to with the Hydroponics one.

Also, your setup is too clean. Water will drip, spill, the pebbles will fall. Looks really nice, though.

About 5 years ago, I worked with a Climate Research Scientist friend, growing exotic plants in dutch-buckets, tower aeroponics, and rack mounted red-lit setups to induce Vitamin B-12 (only found in meat, so deficiencies develops in vegetarian) to Spinach trying to produce Super Spinash.

Is that a subtle 5th Element reference in the crontab?

This is fun!

The following isn’t a knock on anyone doing cool stuff like this: I’ve avoided any sort of tinkering and automation of my gardening because I find gardening to be a slower-moving, meditative escape from technology. My brain shifts into a different mode (almost a flow state?) when I’m out working in the soil and tending to my plants.

I've also tried a few different ways to grow plants indoors and I'd like to share my experiences for anyone interested. I like to grow indoors since I can do it year round and the environment is clean, stable and there are no animals or bugs (knock wood). Over time, I've gravitated towards low-maintenance hydroponics. Growing in soil needs soil, which is also dirty and so a bit more PITA, and it can harbor bugs.

One setup I had was a vertical (hydroponic) window farm, which looked pretty great, but the roots start to get into the tubing, which I suspect could happen in the rack-mount system too. It also wasn't simple to just take out one plant for maintenance.

A small NFT (nutrient film technique) box has worked very well, requires very little material as substrate and is easy to maintain. Might get problematic if growing the same plants for over a year since the roots can grow a lot and basically partially outgrow the system so the flow of water starts being insufficient and therefore might need at least some trimming and replanting if some of the roots start to suffer.

I'm in the process of trying out deep water culture, which requires even less materials since there's no growing medium, just water, and roots are submerged so doesn't have the same issues as NFT. Probably has it's own problems, though, and air pumps can be loud!

Anyhow, most of my plants are in a passive hydroponics system. "Kratky method" is something a bit similar. I basically replaced soil in pots with clay pellets and manage watering so that I have to water every 2-3 days. Requires clay pellets as the substrate so needs a bit more effort up front, but doesn't require electricity and is more portable when using small/medium sized pots. Pellets can be reused (at least most of them). I also added a short tube for monitoring water level and possible maintenance if I need to wash / flush the pot with the plant in it.

Regarding fertilizing, I rarely do any accurate measurements anymore. I got a few pump bottles and measured how much fertilizer one push gets me and wrote on the bottles how many pushes per litre. I also eye-ball the water color a bit since I know how it should look like.

Oh, and the plants that have done well for me, and can grow for a long time with multiple harvests (so no lettuce): peppers, cherry tomatoes, cucumbers, trying some small strawberries

Yo. I successfully did outdoor aeroponics with insane temperatures in the root chamber (near 40°C/100°F). My secret? I grew 'Virginia Gold' tobacco.

> Farmers discovered that bright leaf tobacco needs thin, starved soil, and those who could not grow other crops found that they could grow tobacco. Formerly unproductive farms reached 20–35 times their previous worth. By 1855, six Piedmont counties adjoining Virginia led Virginia's tobacco market

https://en.wikipedia.org/wiki/Types_of_tobacco

This is one beast of a plant. My plants stayed alive when I stopped spraying water in September and only died because of frost in late December. They were about 40 cm high due to the small volume of the root chamber.

Anyway it's a great choice for an outdoor aeroponics setup.

I know this was about the journey, but for anyone interested in home hydroponics (without the journey of building it), I have had a Gardyn[1] for 6-7 years. It works well. It has a 6 gallon (20 liter) tank and a couple of strong vertical growth lights, in a sleek package that looks good in the home. Plants are fitted into pods, in standard-size rockwool blocks that you can get from any grower shop.

The fact that it works at all after a number of years, is surprising to me, given everything that goes on with it: You've got a moist environment with water pumped through it multiple times a day, fertilizer in the water crusting up in places, living plants with their roots growing into the pipes, algae growth, and a lot of parts that are shuffled around often.

There might well be other systems around these days that are the same or better, I wouldn't know, the Gardyn is just what I ended up with when I researched it years ago and I'm happy with it. For downsides, seeds are expensive from Gardyn, but you can plant your own. I do buy some from Gardyn because they have a big selection, and they usually come out good, which regular seeds often don't for whatever reason. They try to push their subscription service but I don't need it, so don't use it.

Hope this doesn't come off as advertisement, as I said there may well be better options (would like to hear about them), but this one works for me for a pretty hassle-free experience.

[1] https://mygardyn.com/product/gardyn-home-kit/

Singapore is currently claiming title of "world's largest (and tallest) indoor vertical farm" with a five story, two hectare automated racked site (Jan 2026):

https://www.youtube.com/watch?v=VJuo6Te1fM4 (2.5 minutes)

Years ago, when California had a really severe drought, I saw a large version of this to grow grass for horses. It had a stack of trays with lights, and each day, you harvested one tray, fed your horse, and replanted the tray. It was only cost-effective when grass hay was really expensive.

What's the idea behind not using capital letters?

I also built something similar. In the end I appreciated the services our nature provides to us even more. Replicating all this artificially is really hard and energy intensive. Planting and growing plans outsides is fun and rewarding; adding all the tech in the end felt like a big waste of resources.

My motivation to work on such a project was my disbelief in human mankind to keep our planet earth habitable.

So:

    1. Convert acres of agricultural land into a datacenter.
    2. Put plants inside.
    3. ???
    4. Profit?

I found growing my own produce to be a great way to appreciate farmers and my local supermarket.

Always lettuce. If someone can figure out how to grow something with a dense and full nutrient profile then there might be something to vertical farms.

Any of the billion guides to growing hydroponic cannabis can teach you how to do this in a vertical rack without issues. Neat write up though.

FWIW I've found ebb and flow systems work fine without the aerator in the water, as the roots get plenty of water during the ebb cycle.

I played around with hydroponics. in the end, they never ended up better than dirt. with dirt you have to water it, and fertilize every few months, but that's it.

with hydroponics, every week I was refilling the water, and adjusting the EC and pH. The end result was very similar to what dirt got me

Setting aside the DIY and hacking spirit of the project, let's remember that, with the commonly accepted figure of 2,500 kcal/day for an adult male, a whole iceberg lettuce (~600g) provides about ~87 kcal which is roughly 3.5% of what one's need.

I am here for exactly this kind of surprise. Nice work, HN!

Looks great! It could be nice to have an integrated temperature control solution that keeps your servers cool and your plants warm.

This is the best thing so far on the internet I have read this year. Thanks.

I just love the simplicity of a cron job control system. This is so fun.

From someone who grew a lot of weed in closets, nice work!

cron and ssh is the worst way to control the pump motor. If the network is interrupted the pump will be stuck on until the next cycle.

I wonder if flood and drain would work with orchids.

I do that manually with my plants twice a week, they have flowers almost all year, but it's a chore to bring them out, flood them, make them drain and bring them back home.

Also my wife always yells at me because I always wet the floor in the process.

All lower case, instant won't read.