Build & Grow Instructions

Shopping List

Press the + on the list items for a direct link to buy online

Control Box Parts

ppm sensor - $79

6x dose pump - $12.99 Ea. / $77.94

pH Sensor kit - $25

Heatsink fan - $17.99

Relay Board - $15.99

5V Power Supply - $13.99

12V Power Supply - $12.99

Raspberry Pi Zero W - $10.99

Waterproof Temp Sensor - $9.95

power cord - $8.53

temp. & humidity sensor - $6.95

heating pad - $2.27

4 Inch Touchscreen

4x LED lights - $5.95 ea. / $23.80

5MP Camera - $9.77

door sensor - $3.95

Keypad - $3.95

Build Cost


Grow Box Parts

cabinet - $79

reflective panda Film - $11.00

300W Full Spectrum LED Light - $40

Carbon Filter Fan - $20

6x Plastic Bottle Bolders - $7

Hydro Bucket Kit - $45

Drip Irrigation ring - $9.75

Humidifier Cap - $7

Casing For Heatsink Fan - $7.50

Casing For Controller - $12


Build & Prepare Your Box

Build The Controller Box

Connecting It All Up

How to Grow

Quick Hydroponic Theory

Hydroponics simply means growing in water.

By growing in water, roots don’t have to spread out and search for nutrients or water. This means wasting less water and growing healthier, happier plants in less time. Think of it as the ferrarri of grow systems.

How is this possible without drowning the roots?

Growers use air pumps attached to air stones within the water reservoir that create bubbles to oxygenate the water and roots. Think of it as a spa for your plant’s roots.

This supplies both H20 and Oxygen to the plants, but what about nutrients?

Liquid nutrients (designed specifically for hydroponics, not soil) are added directly to the reservoir water. We measure the amount of nutrients in the water in PPM, or Parts Per Million.

A key aspect of growing in water is making the pH (Acidicty or Alkalinity) of the reservoir water the same as most soil – which is around 5.6 pH. We do this by adding pH solution to the tap water in the reservoir which brings the alkalinity down and increases the acididty. Tap water is around 7 pH in the United States.

 Nutrients and pH solution are added to the reservoir, but how do you avoid it getting mucky?

No one likes gross water more than algae. Growers have different methods of keeping their reservoirs clean, but here at HARVST we recommend going the natural way – using a microbe tea made from compost. You can either make your own or buy it online (check out our growing supplies). The microbes in the tea thrive in the reservoir environment and will out-compete other harmful things, like algae buildup, while also helping your root growth and nutrient delivery.

Another factor in avoiding algae buildup is making sure there is plenty of dissolved oxygen, which is accomplished with the air stone in your reservoir. Those little bubbles do a lot of work!

We also recommend completely emptying and replacing the water in your reservoir every 2 weeks to be safe, and cleaning any tubes and air stones with hydrogen peroxide and rinse off with water if they look like they need it.

If the plant is growing in water, what’s supporting it and how do seeds sprout?

Hydroponic growers use what are called “growing mediums” to replace the support and seed cushioning that soil otherwise provides. These growing mediums are held within the net pot lid on the top of the reservoir. We recommend starting with a rockwool cube and clay pebbles, but feel free to experiment with other mediums if you feel adventurous.

Rockwool is very similar to soil and is actually spun from molten rock. Seeds are planted directly into the top hole in the rockwool cube. Because rockwool shares the cushioning ability of soil, it’s a perfect place for your seed to start life. The thing to understand about rockwool is that it is a wicking medium. This means if you place a rockwool cube on a thin layer of water, it will wick up the water droplets throughout itself until it is completely moist. This is important to understand to avoid having the water line of your reservoir too high so that it touches the rockwool cube sitting in the top of your net pot, as it will always stay wet and drown your seeds, or get moldy.

That’s where clay pebbles come in handy. Unlike rockwool, these little guys don’t wick, and because of their round shape, they create lots of little gaps in your net cup for roots to grow through to the reservoir. Clay pebbles are placed at the bottom and around the rockwool at the top within the net cup.

How do seeds get water if the reservoir is below them?

Good question! Because seeds don’t have roots, and therefore can’t take in water from the reservoir, we use a drip irrigation ring which pumps water from the reservoir, misting your rockwool cube. This allows excess water to drip off the rockwool and back into the reservoir, making sure the rockwool doesn’t stay too wet.

We’ve learned a lot!

You now have everything you need to wrap your head around how a hydroponic system works and start growing yourself. Have a look at our list of growing supplies below to stock up on goodies, then keep scrolling for more information on planting your first seed.

Growing Supplies

Press the + on the list items for a direct link to buy online

Planting Your First Seed

So you’ve got your supplies – are you ready to create life?

1. Fill your reservoir with water until the water line is about 2 inches above the bottom of your net pot.

2. Place your reservoir back in the box and secure the lid. The water will now be automatically adjusted to the right pH and some microbe tea will be added.

3. Break off 1 rockwool cube and place it at the bottom of the net cup to soak for a few minutes.

4. Remove the rockwool cube and place it on a paper towel.

5. Rinse off a jar full of clay pebbles, these are often coated in dust from packing and are best to give a nice rinse until the water runs clean.

6. Fill the net pot with clay pebbles until about 1 inch above the waterline.

7. Plant your seed(s) of choice in the hole in the top of the rockwool cube. For large plants, only 1 seed is needed. For some smaller plants like herbs, feel free to place a few in the hole – there is plenty of room for them in the grow box.

8. Tear a tiny piece of rockwool from an outside corner and cover the hole gently to make sure no light is reaching the seed. You can also just sprinkle in some vermiculite listed in the optional part of the growing supplies list instead.

9. Now place your rockwool cube on top of the clay pebbles in the middle of your net pot, covered seed side-up.

10. Surround the rockwool cube with the rest of the clay pebbles so that only the top edge is visible. 

Youre all done! Go ahead, close the box and give your seed a few days to germinate. Leaving the box closed will help the seed remain in total darkness. To determine certain factors like what light cycle to use at what plant stage etc, there is plent of additional plant specific information available online.

Troubleshooting Your Grow

My Seeds Never sprouted

Seeds are imperfect, like all elements of nature. If they don’t sprout the first time, try a couple more times. All seeds need is moisture and darkness, so there aren’t too many variables at plat here. Still having issues after 4 failed seeds? Contact the seed company and they will usually send you a fresh batch.

My Seed Sprouted But Died

Sprouted seeds need 2 things, light and water. Make sure you have light on the sprout once it pops out of the drywall. Overwatering is more common than under watering. Make sure your rockwool remains moist, but not wet. Wilting is a sign of both under and over watering.

I want to put a plant from soil into my hydro system

Although putting a plant that’s been in soil into a hydro system is possible, we don’t recommend it for best results. It’s very hard to rinse off every bit of soil from the roots. Any remaining soil can gunk up your reservoir and airstone and any pests carried in the soil might make their way into your system.

My plants leaves are getting lighter green or yellowing at the tip

This is usually a sign of nutrient burn, meaning there is too much nutrient content in the reservoir. Empty and refill your reservoir, and set your PPM value lower. Your plant should recover nicely if this is caught early.

My plant seems very dark green

This is a sign of your plant having too much nitrogen stored in the leaves. Empty and refill your reservoir and lower your PPM. Your plant should start to look a more normal shade of green within a week

Algae is growing on my clay pebbles or rockwool

This is usually caused by light. We advise cutting a square piece of aluminum foil and poking a hole large enough for your sprout in the middle of it. Place if over your net pot so it covers the clay pebbles and rockwool, and your plant can grow through the hole. We advise you do this after the roots hit the reservoir and you no longer need to top water the seedling.