Hydroponic systems can help you grow marijuana faster than using a traditional soil method. It’s harder to grow hydroponic weed, but once you get the hang of it, you can raise larger crops faster with less effort.
Many growers recommend practicing before you try it. For example, plant cannabis in soil and grow it that way to get a feel for it. Or else grow something like lettuce or tomatoes hydroponically as a test run.
If you’re ready to jump in and get started with your own hydroponic setup, let’s take a look at what you’ll need.
Table of Contents
- 1 What you need to grow hydroponic marijuana
- 2 Basic overview of how to grow cannabis
- 3 Types of hydroponic systems for growing marijuana
- 3.1 Deep Water Culture, aka Hydro Pots
- 3.2 General Hydroponics Waterfarm
- 3.3 Deep Water Culture (DWC) Hydroponic Bucket Kit 5 Gallon, 6 inch
- 3.4 AutoPot 4pot System Gravity Fed Watering System. Hydroponics and Traditional Gardening
- 3.5 Ebb and Flow, aka Flood and Drain
- 3.6 Viagrow V4X4COMP Ebb & Flow Hydroponic System Tray, 4′ x 4′
- 3.7 Top Feed
- 3.8 Nutrient Film Flow Technique
- 3.9 General Hydroponics RainForest 66 Aeroponic System for Medium to Large Size Plants
- 4 Growing mediums for hydroponics
- 5 Tips for growing healthy plants
- 6 How to test pH acid levels
- 7 How to fix pH levels that are too acidic or alkaline
- 8 How to stop root rot
- 9 Nutrients for healthy cannabis growth
- 10 Get the low down on growing weed
What you need to grow hydroponic marijuana
Here are the basic things you need to raise cannabis in a hydroponic garden:
- A space for growing, like a grow tent
- Lamps that mimic sunlight
- “Soil” like coco coir or peat
- pH tester for acid levels
- Timer to control the lights
- Ventilation if you use hot lamps like HPS and if you need to control odor
- Seeds or clones
Each plant you grow will result in one to three ounces of marijuana, depending on factors like the strain and how healthy the plant is.
Basic overview of how to grow cannabis
Whether you choose the more popular Sativa for its high, or Indica for its calming and healing power, most of the growth process is the same. You might trim the top of an Indica to make it bush out more, but the way you water and feed both kinds of plants is the same.
First, check the temperature in your grow room. The best range for cannabis is between 80 and 85 degrees F, but no more than 90 degrees.
Second, use filtered or pure well water to avoid feeding your plants chlorine and fluoride. Check the pH to make sure the water is slightly acidic, between 5.5 to 6.5, with 6.15 being about right.
Third, follow the instructions of the light you have with regards to the proper height and coverage. Hang the light at the correct distance from the tops of the plants and make sure the light reaches out to the edges of your grow area. This is where a grow tent lined with Mylar helps reflect the light back onto the plants.
Run the light for the necessary amount of time according to the growth phase of the plant. For germination, you don’t need light. Once you have sprouts, you can run the light 18 hours a day until they reach half of their final height (which depends on the strain of weed). Then to flower, you only need 12 hours of light per day.
One or two weeks into the flowering stage, sex the plants to separate males and females. You don’t want them to reproduce if you aren’t trying to get seeds. Females get white hairs and males get balls. Yes, balls. You can’t smoke males so get rid of them. They’re only good for pollen.
About two weeks before you harvest, cut out the nutrients and only feed the plants water. This cuts down on any nutrient flavoring.
When harvesting, trim the plants with a bud trimmer or by hand and dry them. Store them in an airtight container for two weeks to a month to cure.
Now that we covered the basic way to raise cannabis, let’s look at hydroponic systems.
Types of hydroponic systems for growing marijuana
Deep Water Culture, aka Hydro Pots
For beginners, Deep Water Culture is cheap and easy to put together and use. It has three parts:
- a bucket or reservoir where the water-based nutrient solution is stored
- another basket or mesh with peat or rockwool “soil” for the roots to grow through down to the nutrient solution
- an air stone like from a fish tank providing air to the nutrient solution
You need one Deep Water Culture unit for each plant you plan to grow. Imagine a five-gallon bucket with nutrient-rich water at the bottom, then a basket filled with peat moss or clay where the weed is planted, then the air stone bubbling down inside the liquid at the bottom.
Then imagine that you have more than one plant, so you can link all these individual buckets with irrigation tubes into a single reservoir that sends the nutrient water out to feed each plant.
Two things you need to be careful about are contamination and stagnant water. Make sure that the nutrients at the bottom of the main container are protected from light and contamination, and that the air stone doesn’t stop working.
Here is an example of a good Deep Water Culture system for a beginning grower.
General Hydroponics Waterfarm
General Hydroponic’s Waterfarm is a simple and inexpensive hydro pot perfect for a beginner grower. Even better, you can link each one of these units into a larger configuration to grow more plants at once.
It comes with a 2-gallon container reservoir, a smaller basket container, clay pellets, an air stone, an air pump, nutrients, and the necessary tubing including drip feed.
The only thing to watch out for is the pH or acid levels at the beginning as your young plants start to grow. Be sure to test and make adjustments as needed.
Deep Water Culture (DWC) Hydroponic Bucket Kit 5 Gallon, 6 inch
PowerGrow System’s Deep Water Culture 5-gallon bucket kit is great for larger kinds of cannabis. It takes up more floor space but handles humongous strains like Big Bud and Brian Berry Cough.
The PowerGrow System comes with an FDA-approved food safe 5-gallon bucket plus basket lid, air pump, air stone, tubing, and Rockwool plugs as a growing medium.
We like this setup because it has a water level marker and a bucket drain. It comes with a 1-year warranty. One note of caution—when Rockwool is dry it’s irritating to skin. Use gloves to handle it until it’s properly moistened.
AutoPot 4pot System Gravity Fed Watering System. Hydroponics and Traditional Gardening
AutoPot comes with one large 12-gallon reservoir and 4 smaller pots that hold 3.9 gallons each. It doesn’t come with air stones or potting medium but you can add those.
This setup is gravity-fed so it only sends nutrients when the plant has used enough in its own pot to make room for more.
One thing to watch out for is contamination in the central reservoir. If that happens, all your plants will suffer.
Besides Deep Water Culture systems, which are typically the simplest and least expensive, there are other ways to grow with hydroponics.
Ebb and Flow, aka Flood and Drain
Ebb and Flow systems soak and drain the roots of your plants. You won’t have to worry about using air stones because the water doesn’t stagnate. You will need a timer if one doesn’t come with the system. Again, if your central reservoir has a parasite or problem, all the plants suffer.
Viagrow V4X4COMP Ebb & Flow Hydroponic System Tray, 4′ x 4′
Viagrow sells a four-foot by four-foot Ebb and Flow System complete with tray and stand, potting medium, timer, pump, and tubing. The 25 pots included in the box hold one gallon each but you can replace them with larger pots.
Top Feed systems use reservoirs like Deep Water Culture, but a pump on a timer sends nutrient solution raining down over the roots. Anything that drains away goes back into the reservoir.
One thing to watch for is how well your pump functions. If it breaks down, all your plants will go thirsty.
Nutrient Film Flow Technique
Nutrient Film Flow Technique systems use something called a capillary mat instead of moss, clay, or Rockwool as the “soil.” These porous mats keep the nutrients constantly circulating around the roots. The plants get fed, but not drowned, and nothing get stagnant.
Aeroponics with Misting
With Aeroponics and Misting, you’ll have a rain forest-like atmosphere for your plants. This is not great for growing in a closet or spare bedroom unless you have a very good isolating grow tent indeed.
Plants hang in baskets and their roots get misted on a schedule. This makes for really fast growth but you have to monitor every closely. If the pH gets out of whack or the plants aren’t getting the right mix of nutrients, the consequences build up quickly.
General Hydroponics RainForest 66 Aeroponic System for Medium to Large Size Plants
The RainForest 66 Aeroponics System from General Hydroponics is a convenient all-in-one setup to grow your weed. It comes with a 17-gallon reservoir, a sprayer, 6 plastic containers with CocoTek liners, and a 3-Part Flora Kit. The system aerates the nutrient solution before spraying it over the plant roots.
One thing to consider is that you need to watch for parasites like aphids if you don’t have this setup isolated from pests. Another consideration is the size of the pots—they are only six inches in diameter.
Growing mediums for hydroponics
There are a wide variety of “soils” you can use in place of real dirt. These materials are superior choices for hydroponic growing. Let’s take a look at each kind.
Peat is a popular base because it’s cheap and loaded with minerals. The most common types you’ll see are peat moss and humus.
Sphagnum moss is lightweight and it holds a lot of water. It’s more expensive than peat but it works better for hydroponics.
Coco coir is made from shredded coconut husk. Sometimes it’s formed into croutons. It’s super-absorbent and retains water very well.
Rockwool, aka, mineral wool, is spun into fibers and formed into cubes or slabs. It keeps water while letting air to penetrate to the roots. It’s alkaline by nature, so you may need to treat it before using it.
HEC pellets don’t have any nutritional value like moss, but it works great in hydroponic systems because it drains well and lets the plant roots get oxygen. It’s heavy enough to keep young plants in place during watering.
Vermiculite is a mineral used as an additive for soilless mixes. It holds moisture and nutrients very well. Perlite is another absorbent additive often seen mixed in with coco coir and peat.
Tips for growing healthy plants
Use these tips from expert growers to help your hydroponic experience go smoothly.
- Water your plants every couple of days when they are young, then plan on watering them once a day when they are flowering.
- Use a hygrometer to check the moisture levels or water when the top of the potting substrate feels dry.
- Watch the leaves to see if they wilt or droop—those are indicators of too much or too little water.
- When plants are flowering, some leaves may turn yellow and drop off. Stop giving nutrients, just water, because in a week or two you’ll be harvesting.
- Harvest when one-half or three-quarters of the white hairs have turned yellowish brown and when the trichomes have gone white or yellowish.
- Late harvesting makes for more relaxing marijuana.
- When trimming, don’t leave on leaves because they don’t have much THC. Use leaves to make cannabis oil or butter.
- You can tell when your buds are dry enough because they will snap off cleanly instead of bending.
How to test pH acid levels
Having the correct amount of acidity is essential for growing healthy cannabis. The right pH means nutrients get absorbed properly. Here is a brief overview of how to test pH levels.
Soil pH ranges from 1 to 14, with 1 being very acidic and 14 being very alkaline, with 7 being neutral. The ideal for weed grown hydroponically is 5.5 to 6.5, just a little acidic. (In dirt, you’ll want between 6.0 and 7.0.)
You can test the levels in two places—the nutrient solution itself and the “soil” where the plants are growing. Use a tester pen, strips, or a liquid solution to get results. You’ll take samples of the nutrient solution or the soil and use the tester to see what the acid level is.
How to fix pH levels that are too acidic or alkaline
Don’t panic if your levels vary a little from day to day. The weed can handle it. But if you go below 5.5 or above 6.5 when you’re growing hydroponically, the consequences add up fast. It’s best to fix the levels as soon as you can.
General Hydroponics sells an easy-to-use pH Control Kit. This kit even includes a pH tester so you don’t need to buy another one.
Some experienced growers have learned how to adjust pH levels with household items like baking soda and vinegar, but we don’t recommend this for new growers.
How to stop root rot
Root rot is a fungus that can quickly spread through all of your plants if they are on an interconnected system. You’ll see signs like wilting leaves that turn yellow. The roots will not look white or creamy, they will be brownish and smell terrible like mildew or rot.
You can prevent root rot by making sure you don’t overfeed or water your weed. Keep water temperatures below 72 degrees. Clean your system according to the manufacturer’s instructions. Remove any dead plant matter.
You can also add beneficial bacteria to your nutrient solution. Plus, there are products called “root controls” that kill the fungus. Some growers spray the plant roots with copper treatments or clove oil. Be careful if you use hydrogen peroxide—it’s not the best choice because it kills beneficial bacteria.
Make sure your reservoir is protected from light and too much heat. If it’ properly sealed the fungus has a harder time invading.
If you have many plants, you may choose to remove the affected plant and watch the others to make sure they don’t get sick.
Nutrients for healthy cannabis growth
So we’ve mentioned nutrients like a zillion times and maybe you’re asking yourself what those actually are. Our favorite at the moment is a product from General Hydroponics. It’s something that NASA uses to grow plants (but not weed) in space. It’s a favorite product for people who raise herbs for essential oils, too, because it’s all organic.
General Hydroponics General Organics Go Box
The General Hydroponics Go Box is a great assortment of organic nutrients for marijuana (and other plants). It even comes with instructions and a schedule to teach you how to use them.
The box contains pint bottles of BioThrive Grow and Bloom and 8 ounce samples of CaMg+, BioRoot, BioWeed, BioBud, BioMarine, and Diamond Black. You can try them all and see your weed grow like crazy.
Get the low down on growing weed
Check back soon for more reviews and guides. Happy growing!