Aug 18, 2022
DIY Hydroponics on the cheap
You don’t need to spend thousands of dollars to grow salad, tomatoes, or strawberries hydroponically. Here’s how to do it for less than $150, everything included.
As part of my day job at TechCrunch, I get a surprising number of pitches for companies doing at-home hydroponics systems. They have a few things in common; they typically have a subscription model so they can send you seeds and nutrients. The setups themselves can also be eye-wateringly expensive.
Hydroponics isn’t magic; you can build your own in a few hours. Here’s a complete guide, including links to the bits you need to buy. If you follow the steps, you’ll have your own hydroponics system for under $150 — and that’s everything you need, including seeds, hydroponic food, etc.
Use this guide if you like, or use it as a starting point for your own DIY grow operation.
I have built hydroponic systems, fountains, and beer brewing equipment myself in the past, so I ended up assembling a lot of the parts of this system from stuff I had lying around. Get creative, that’s part of the fun!
A bit of theory
Hydroponics is super simple. In a nutshell, it’s ‘growing stuff without soil.’ First, your seeds go in a growing medium (I’m using rockwool). Once they’ve sprouted, the rockwool goes in a little basket in a bucket of water. From there, you need a pump (to keep the water circulating).
Because there’s no soil, the plants can’t get their food from the earth, and you must add nutrients to the water.
If the water is stagnant, the plants will soak up all the oxygen from the water. The beauty of this system is that the water is moving around and has a chance to pick up some oxygen along the way. Of course, you can also add oxygen to the water separately — but we’ll cover that in just a moment.
That’s it. Plants have roots. Roots go in the water. Plants are happy. You eat the plants (if they are edible) or look at them (if they are pretty), and that’s all there’s to it.
Let’s get to building.
Tools you’ll need
- An electric drill or screwdriver is helpful.
- Drill bits + a 2” hole saw ($9) is helpful (although you can use a knife to cut holes in things if you want to save money)
- A sharp knife. An X-Acto blade ($9) works great.
- Some caulk ($7)
Shopping list
To the hardware store we go! Below is a bunch of Amazon links that shows you what you need, but for this sort of thing, you can often find the hardware and items you need more cheaply in your local hardware store.
Also, the links below are so-called affiliate links. That means that if you do choose to buy something, Amazon gives me a couple of pennies. That doesn’t affect the things I’ve chosen to recommend, and, in fact, I suggest you go visit your local store to get what you need… But I figured it was fair to disclose the dastardly nature of these links.
The core system
- Solar water pump ($20) There are a lot of options for the water pump; any aquarium pump should do. I like using one that’s solar-powered because it means I don’t need access to a power socket. It also means that the system runs during the daytime and stops at night. That makes sense to me! You can buy any submersible water pump. Don’t go crazy — the first 4(!) pumps I bought were way too powerful. A little goes a long way here. A cheap $14 pump probably does the trick.
- Five-gallon bucket with lid (This will set you back around $6 from any hardware store, or $10 from Amazon). The 5-gal bucket will become your water expansion tank.
- 12x one-gallon buckets with lids ($33). This is where your plants will be bathing and enjoying the sunshine. You can also use 3- or 5-gallon buckets for larger plants, but I like the convenience of having multiple, smaller growing vessels. Make sure you get lids, because you’ll need ’em. (Alternatively, if you want to grow large plants — tomatoes or marijuana, for example — use 5-gallon buckets for that, too; you can buy special lids for them ($8.50 each) that already have a grow basket in them.)
- 50x two-inch plastic grow baskets ($9) This is where your plants will sit.
- Silicon tubing ($10). The tubing is there to lead the water around your system.
- Pack of 6 hose barb fittings ($14). You don’t strictly need this — there are cheaper ways of attaching silicon tubing to buckets. However, using proper barbed fittings makes life so much easier; I probably wouldn’t make do without it. You’ll need two per bucket, so a kit of six is enough for three buckets.
- Hydroponic plant food ($26). This stuff lasts quite a while, but if you want real bang for your buck, get the 1-gallon bottles instead ($84)
- 1.5-inch rockwool grow plugs ($10 for 28). This is the medium where you’ll be growing your seeds
- Leafy green seeds ($18 for 4,000). This is where the magic begins!
Upgrades
Here’s a bunch of things you can add to the setup, but you don’t need to worry about it from day 1. Instead, build a more straightforward system first, and if you want, add some fancier upgrades later.
- Air pump ($9) and Air diffusion stones ($7) to oxygenate the water. Because the water is moving around, you probably don’t need to oxygenate. Having said that, plants are much happier if the water has a bunch of oxygen, so this would be my first upgrade once you’ve got the basics down.
- Hydroponic pH control kit ($20) I bought one of these, but after a while, I realized that the pH in the water stayed pretty much in range without much help from me. I also refresh all the water every month or so anyway, so perhaps it isn’t worth it. On the other hand, if your plants grow slowly or seem unhappy, give it a whirl.
- In-line filters ($8 for 10) I don’t know if these are strictly necessary, but I noticed that sticking filters in the water lines helps control algae, and keeps the water cleaner, which should mean that the water pump keeps working for longer. Again, if you change the water frequently, you probably don’t need these.
- Grow lights ($40) My current hydroponic system is outdoors, so I let the sun do the shiny part of the plant growing. I’ve had it indoors in the past, and it works great, but take this from me: If you want to move it indoors, test everything thoroughly (flooding outdoors is annoying, flooding indoors is expensive and annoying), and slap some lights and a timer on there.
- Solar power: If you want to go green, let the sun do the power delivery, too. A solar panel ($100)+ battery ($80) + charger controller ($15)+ inverter ($43) — This is all stuff I had laying around from a trip to Burning Man and now keep handy in case there’s a power cut. I probably wouldn’t buy any of this stuff, especially for a hydroponic setup, but if you want to have some fun with it all… Go for it! (A less DIY version that includes the controllers and inverters etc, in a user-friendly package would be to use a Jackery ($300) and a solar panel ($170), but again — that makes things real expensive real fast.)
Putting it all together
At the very basic, the system consists of a water reservoir where the pump lives and one or more buckets that are your hydroponic system — that’s where the plants go.
Here’s an overview:
In the middle of the picture — the big five-gallon bucket with the lid propped open, is my expansion tank; as long as this one stays full, the system will have enough water to keep running.
My hydroponic grow stites are the two smaller buckets on the wall (one closed, one open). I have them at different levels on purpose, so gravity can help keep the water flowing.
Kinda hard to see in this photo, but the last one-gal bucket on the right has a tube running from its ‘out’ port back into the expansion bucket. That way it stays a closed system, and the water just cycles through the buckets.
On the left, the solar panel powering it all. The battery, controllers, and inverters are behind the solar panel. As I mentioned, this is all optional.
The little bucket on the ground contains the air pump. It’s in a bucket because I’m not sure the air pump likes water, so it seemed to make sense to keep it more or less water proof.
Building the system
Use a hole saw or a template and a sharp knife to make a hole in one of the bucket lids:
I decided to put mine off-center, because the idea is to be able to put two or even three baskets in the same bucket. I figured I’d start with one to iron out any kinks, and then potentially add another later on.
Drill a hole in the top rim of the bucket, and install the barb fittings. Use some caulk to ensure it all stays water proof:
Then install the tubing. There’s not a lot of pressure on the water here, so if your barbs are the right size for the tubing, you don’t need clamps or caulk to keep this water-proof. That’s helpful, in case you need to disassemble the setup (I often do, to clean or change the water)
If the surface the bucket is on isn’t perfectly straight, you’ll want the ‘out’ barb on the lower side, and the ‘in’ barb on the higher side. This will help prevent the water from overflowing.
In my first version of this, the water was too stagnant — it just flowed into the bucket, and out the other side. Great for the plants, but it didn’t help move the nutrients around as much as I had wanted.
I found a solution: Add a short length of tubing to the ‘out’ hole on your bucket:
Why this works — The water comes in from the left, either from the pump, or from another bucket. On the right, I have a short length of tubing. This acts as a ‘straw’, which means that the bucket will fill until the highest level of the ‘straw’, and then gravity will take care of draining the bucket until the straw is no longer submerged.
This means that the buckets will always be filling and emptying a little. The roots of the plants will stay in the water, and there’s enough movement to ensure that nutrients and oxygen keeps flowing. This also gives your system a little bit of leeway to ensure that it doesn’t easily overflow.
Put the water pump in the expansion bucket, connect the tubing to the pump, and turn on the power. Boom! You have a working hydroponic system!
Plant your seeds — You’re going to want get some rockwool, and start sprouting your seeds indoors, until they are big enough to go into the hydroponic system.
- Use a toothpick to poke 4 little holes in the rockwool.
- Place a seed on top of the hole, and push the seed in, about half an inch (1.5 cm).
- Place the rockwool on a plate, and pour a little bit of water on top of it.
- Keep an eye on it — add a little bit of water daily. You don’t want it water-logged, but you don’t want it drying out either. Ideally, the plate stays (mostly) dry, and the water saturates the rock wool.
- Keep at room temperature. Supposedly 80F/25C is perfect, but seeds find away, in my experience.
- Depending on the seeds, you should see sprouts in 5–7 days.
- When the roots start poking out of the bottom of the rock wool, you’re ready to move your little baby plants to the hydroponic!
Once your plants are in the hydroponic, they’ll probably be a little shocked. It’s bright outside, and there’s a lot more temperature variety. Give them a bit of time.
Once they catch, have figured out what outside life is like, and start growing properly, cut off the weakest-growing saplings — you want one plant per rockwool cube, ideally. For smaller plants, you can try to grow two in the same cube; your mileage may vary.
Troubleshooting
There are a few common issues I’ve come across…
Overflowing
Reduce the water flow — The most common problem I’ve had with this system is that the water pump is too powerful. If that happens, it pumps more water into the first bucket than the ‘out’ line is able to carry away. It’ll flood, and make a mess.
The solution is obvious: reduce the water flow. Some aquarium pumps have a dial you can turn to reduce the flow, but you can also add a hose flow control clamp (They cost $5.50 for 2 on Amazon, which is a ridiculous rip-off. They’re around $0.50 or so at hardware, home brewing, or hydroponic stores. Ali Express has them for $35 cents for 2). These have multiple notches in them so you can fine-tune how much water flows through the hose.
I have a whole bunch of them somewhere, but I couldn’t find one… So I made my own, out of a broken chopstick and a couple of zip ties:
The water doesn’t flow properly through the system
Check the heights of the in and out barbs — If you’ve used the little ‘straw’ tip to keep the water level flowing up and down throughout the day, your buckets need to be at slightly different heights. Specifically, the ‘in’ barb on the second bucket needs to be lower than the straw on the ‘out’ barb on the first bucket.
It only needs to be an inch or so, but if the ‘out’ barb is lower than the ‘in’ barb, the system won’t work.
Growing the system
If you are running a huge system with lots of grow sites, you may need more than one expansion tank (if so, connect them with a length of hose near the bottom of the bucket), or a larger expansion tank.
For extra green points, collect rain water (or gray water from your shower) and use that to fill your expansion tank.
I’ll keep updating this post as the hydroponic system evolves and as I learn more about what works and what doesn’t work as well!
Any questions? DM me on Twitter or leave a comment below.
