If you want to have more control over the supply of water, nutrients, and oxygen to your cannabis plants, then the hydroponic grow method is for you.
Hydroponics involves using a soilless yet nutrient-rich medium to grow your marijuana plant. This approach has a lot of perks, especially if you live in a place like Australia, where the climate is tricky.
As a new grower, you could hesitate to use hydroponics because it seems more complicated than growing in soil.
But the hardest part is just getting started. Once you’re set-up, caring for your plants becomes much easier.
Follow this guide, and you’ll do great! In the sections ahead, we have carefully detailed the A-Z of hydroponic cannabis growing.
Key Takeaways
- To grow cannabis using the hydroponic technique, use a mixture of water and nutrient solutions as the primary medium instead of soil. You can choose between an active or passive setup to make this happen.
- To get started, you’ll need a hydroponics starter kit, grow tent, carbon filter, and oscillating fan, among other supplies.
- White Widow, Northern Lights, and Blue Dream are examples of cannabis strains that work well for hydroponic growing mediums.
- Nutrient levels should reduce as your plant moves from the vegetative to the flowering stage.
Introduction to Hydroponic Cannabis Growing
Once you understand how the hydroponic medium of growing marijuana works, it’ll be easier to decide if it’s something you want to do or not.
So, before discussing how to set up this system and the tools you’ll need, let’s briefly review the benefits and potential challenges associated with this method of weed cultivation.
How Does Hydroponic Growing Work?
When you grow cannabis hydroponically, you use an inert medium like coco or reservoir water as the primary medium. Hydroponic is the Latin word for “water working.”
This system involves the flow of highly oxygenated, nutrient-enriched water so a desired amount goes directly to the plant’s root.
Benefits of Hydroponic Cannabis Cultivation
Growing hydroponically means plants are in a system that uses a water reservoir to keep them properly hydrated. So, it’s easier to manage the concept of over- or underwatering.
Another advantage is that many weed plants develop faster in the vegetative stage when grown in a hydroponic medium.
This translates to bigger yields and faster harvests, which is the desire of any serious grower.
When growing in a reservoir, nutrients are used more efficiently. The water only needs to be refreshed a few times a month, and once the plant has absorbed most of the nutrients, the remaining water can be discarded.
This approach can save you money on expensive nutrients and is more eco-friendly than a drain-to-waste method.
Also, there’s the school of thought that hydroponically grown buds are more potent and often sell for more at dispensaries.
Challenges Specific to Growing Hydro in Australia
Most people find growing in soil more intuitive because they’re familiar with it from other gardening experiences. This can make hydroponic grow seem challenging at first.
Apart from that, setting up a hydroponic system takes more time and effort than soil.
Also, without proper oxygenation and monitoring, your plants might suffer from root rot.
Setting Up Your Hydroponic Grow System
When setting up a hydroponic grow system, the first thing to do is to pick a growing medium that replaces soil. The chart below explains the four popular options:
| Substitute Growing Medium in Hydroponics | Description |
| Coco Coir | Coconut fibre |
| Rockwool | Volcanic rock with a wool texture |
| Perlite | Volcanic glass |
| Clay Pebbles | Preferably pre-altered to protect pH levels |
Once you decide on the growing medium, you then pick a hydroponic setup of your choice.
Choosing the Best Hydroponic Setup for Your Space
If you’ve ever seen cannabis plants growing with their roots just floating in a reservoir of water, that’s a type of hydroponics called Deep Water Culture (DWC).
But there are four other popular types: Ebb and Flow, Drip System, Wick System, and Nutrient Film Technique.
We will go over the pros and cons in the next sections, as they will determine the kind of supplies and equipment you need.
Different Types of Hydroponic Systems
Hydroponic systems can be either active or passive based on how they are set up.
Active systems use electric pumps to move the nutrient solution and air stones to oxygenate the water. Examples are Deep Water Culture, Ebb and Flow, and Nutrient Film Technique.
Passive systems are simpler. They often use capillary action instead of electric pumps to deliver nutrients to the plants. A good example is the Wick System.
Deep Water Culture (DWC)
If you want a cheap and easy setup for your hydroponic growing, then consider the DWC.
In this setup, the roots of your cannabis plants are encased in a grow pot or bucket that is suspended from a lid.
The roots hang into the nutrient solution in the reservoir container. An air pump aerates the nutrient solution.
This is a popular method for growers new to hydroponic cultivation.
Ebb and Flow
The Ebb and Flow hydroponic system is straightforward and efficient. Water and nutrients flow in and out, bringing fresh oxygen to the plants’ roots.
In this system, a reservoir filled with a nutrient solution is placed below the growing tray.
Using a timer, the solution is pumped up to just below the top of the growing medium for a short period (usually just a few seconds).
The solution then drains back into the reservoir over about 30 minutes. This cycle repeats continuously, ensuring the plants get nutrients and oxygen.
Drip System
In this setup, you fill your growing medium in a large tray and place the cannabis plant directly into the medium.
There’ll be a drip pipe near each plant where an external water tank pumps a constant supply of water and nutrients over each plant.
It is just like the drip irrigation process of growing in soil.
Wick System
In the Wick system, you place a tank of water below a growing tray such that the tray uses several wicks that exit and enter the growing medium. This allows water to flow through the wicks and hydrates the medium.
Nutrient Film Technique
You can use the Nutrient Film Technique for your hydroponic system to grow a shallow-rooted, lightweight, fast-growing weed plant.
In this setup, you place the marijuana plant in a sloped container so water can enter one side and use gravity to exit out the other.
Since the roots dangle, the nutrient solution can return to the tank, making it a continuous process.
Essential Equipment for Hydro Weed
If you’re not investing in a hydroponic starter kit, then it means you want to go the DIY route. We have created a list of the equipment you need to construct a basic indoor setup.
You need to consider the grow tent, lightning and lighting hangers, pumps, reservoirs, timers and metres, oscillating fans, air stones, and air pumps.
Grow tents and lights
If you’ve been growing indoors and are familiar with setting up a grow tent, this shouldn’t be much of a headache.
To set up the right grow tent for hydroponic setup, it has to be lightproof, waterproof, and well-ventilated so it doesn’t trap heat.
The size of the tent depends on the space available, your budget, and how many weed plants you’re growing. If you’re a hobby grower, a 1 x 1 m tent will work just fine. (BudBox Pro and GroWell Horticulture are popular brands).
If you enjoy building from scratch, consider using 19mm PVC pipes for the tent’s frame. They are sturdy and affordable.
The main materials you’ll need for the grow tent are:
- 16 straight pipes for the verticals and horizontals (the length depends on the size of your tent).
- 8 90-degree corner fittings
- 4 T-fittings
- 1 cross fitting
You can find plenty of YouTube DIY videos to guide you through assembling these materials into your grow tent.
For lightning, 400W and 600W bulbs are the most suitable for indoor cannabis cultivation. However, 600W may be too intense for seedlings and cuttings.
You also need to hang the lights at a level. The optimal light height or OLH, is 30–50 cm above the plant canopy.
This means you have to fasten the reflector to the grow tent’s ceiling so it can be easily adjusted and repositioned as the plants mature and grow taller.
Pumps, reservoirs, and timing
The success of your hydroponic growing also hinges on choosing the right reservoir size. The size decision is based on the type and number of cannabis plants you’re growing.
You need at least ½ gallon of nutrient solution per plant. But if you’re growing larger plants, aim for a minimum of 2.5 gallons of nutrient solution per plant.
Meanwhile, you’ll also need a timer to control the water pump (at least for most hydroponic systems).
A heavy-duty light timer (15 amps) works well. We recommend 15-amp timers because 10-amp timers can burn out, and the 15-amp ones only cost a little more.
Quick Tip:
- Use less expensive dial (mechanical) timers instead of the pricier digital ones.
If you’re using the Ebb & Flow (Flood and Drain) systems, drip systems, or aeroponic systems, you’ll need a pump timer.
DWC systems use an air pump that runs 24/7, so no timer is needed. Wick systems don’t use pumps at all.
Air stones and air pumps
Part of the equipment you’ll need to get is air stones. They will help the weed plants absorb more nutrients, which leads to faster growth.
Some hydro systems do not involve roots being submerged in water. Even in that case, you’ll need air stones to aerate the nutrient solution.
Meanwhile, cannabis plants need to absorb oxygen for growth and to avoid suffocation, especially if you’re using the DWC system, where roots are submerged in the nutrient solution 24/7.
This is why you’ll need an aquarium air pump and an airstone in your nutrient solution.
That way, the oxygen the plants absorb is replenished, and harmful pathogens are kept at bay.
As we move through the step-by-step guide from germination to harvest, you’ll discover additional essential tools for successful hydroponic growing.
How to Grow Hydroponic Weed: Step-by-Step Guide
Follow these steps to kickstart your hydroponic journey. For this guide, we will use the drip system.
Step 1: Prepare the reservoir
The reservoir holds the nutrient solution for your plants. Depending on your space, it can be different sizes and shapes.
Inside, it will have a water pump and an airstone. Connect the air pump to the airstone and set up a drainage line from the grow table to the reservoir.
The water pump will also have a line that leads to the drip system and a power cord.
Step 2: Set Up the Grow Table
The work of the grow table is to collect any extra plant water and return it to the reservoir.
When setting up the table, ensure a low spot for the water to drain. That low spot should have a drain pipe connecting to plastic tubing from the reservoir.
Step 3: Add Buckets with Clay Pebbles
Assuming clay pebbles are the artificial grow medium to replace the soil, fill a 5-gallon bucket with clay pellets and place the gallon on the grow table.
Soak the pellets overnight to ensure they’re fully wet.
Drill small holes in the bottom of the bucket so excess water can drain onto the table.
The holes should be just big enough to let water through without allowing the clay pebbles to escape or clog.
Step 4: Set Up the Drip System
Connect the plastic tubing from the water pump to the grow table. Use drip line equipment to create holes in the tubing and extend the drip line to each bucket.
Attach drip line emitters to the end of each line to deliver water to the plants.
We recommend running the system without plants first to ensure everything works correctly. There shouldn’t be any standing water.
The air pump should keep the water in the reservoir oxygenated, and the buckets and grow table should drain excess water back into the reservoir.
Step 5: Prepare a Nutrient Solution
Once your system is working, mix the nutrient solution in the reservoir. Nutrient solutions for hydroponic growing differ from those for growing cannabis in soil.
You’ll find more information on nutrients and how to use them as we progress in this guide.
Step 6: Introduce Your Plants
Before introducing your plant into the clay pellets, you must have germinated them.
Germination and seedling stage
First of all, some cannabis strains are more suitable for hydroponic medium than others.
We recommend opting for strains that don’t grow too tall so that they are easier to manage in an indoor hydroponic setup. You can consider White Widow, Northern Lights, or Blue Dream cannabis seeds.
There are many methods for germinating cannabis seeds, but the popular option for a hydroponic medium is paper towels.
You wet a large paper towel and lightly wrap your weed seeds in between the paper towel.
Place the paper towel on a flat surface, then cover it with a plate to prevent drying. Let it sit for 24 hours.
Then, assuming you’re using rock wool as the replacement for the soil medium, you use your fingers or a spoon to dig a small hole in the rock wool block, then place the germinated seed in the hole with its sprout pointing up.
Ensure the drip line provides moisture to the rockwool and the plant roots.
Vegetative stage
The vegetative stage of cannabis is where the plant’s growth truly takes off, and it typically lasts 3–16 weeks, depending on the strain.
The plant grows taller and wider, develops its roots, and produces more leaves.
They’ll need 18 to 24 hours of light a day to imitate the summer when days are long.
Flowering stage
Many indicators suggest the time for the flowering stage to start, but when the plants become 15 to 46 cm tall and you switch to 12 hours of light daily, they transition to the early flowering stage.
The flowering stage is a period of a weed plant growth cycle characterised by bud growth, terpene profile formation that gives the buds their taste and flavour, and cannabinoids formation (THC and CBD).
It can last for between 6 and 12 weeks. At this stage, you want to keep watering them with pH-balanced, nutrient-enriched water.
Harvesting and curing
Stop giving your plants nutrients with their water for the last 1 to 2 weeks before harvest.
The main signs of harvest time are 50% to 70% amber-coloured pistils on buds and cloudy trichomes.
At the late flowering stage, you also want to adjust the pH level to 5.5-6.0.
When harvesting your cannabis plant, start by clipping leaves that stick out from the buds. Hang the buds to dry for 1 to 3 weeks in a cool, dark environment.
The buds are dry when the stem makes a snap sound as you try to bend it.
You then leave the dried buds in an airtight container for 2 weeks. This is called curing. The purpose of this on your buds is to increase their shelf life and improve their flavour and aroma.
Nutrient Management in Hydroponic Systems
Every hydroponic system requires frequent monitoring. This bothers me with properly mixing and applying nutrients and monitoring pH and EC levels.
Essential Nutrients for Hydroponic Cannabis
Hydroponic nutrients are different from those used for growing weed plants in soil.
If you’re growing your cannabis plant in a soil medium, the essential nutrients won’t include all micro-elements because the soil already provides that naturally.
So, a good hydroponic nutrient should include all these elements:
- Nitrogen (N)
- Potassium (K)
- Phosphorus (P)
- Calcium (Ca)
- Magnesium (Mg)
- Sulphur (S)
- Iron (Fe)
- Manganese (Mn)
- Copper (Cu)
- Zinc (Zn)
- Molybdenum (Mo)
- Boron (B)
- Chlorine (Cl)
The easiest way to get these nutrients in their correct proportions is to buy pre-formulated commercial hydroponic nutrients from local gardening stores in Australia.
But you should also know how to mix and apply the nutrients to match the needs of your hydro setup.
How to Mix and Apply Nutrients: Monitoring pH and EC Levels
It’s impossible to talk about the proper mixture and application of nutrients in a hydroponic system without first considering the EC (electrical conductivity) reading, and then the pH is correct.
The EC reading helps you determine how strong your solution is and how mineral-rich the water is. The more minerals, the higher the EC.
For cannabis, an EC reading between 0.8 and 2.0 is generally appropriate. Younger weed plants need fewer nutrients, while larger, flowering plants require more.
Quick Tip:
- You can convert your EC reading to parts per million (ppm), indicating how nutrient-dense your solution is. There are two standard ppm scales: the 500 scale and the 700 scale.
To convert an EC reading to ppm, multiply it by 500 or 700, depending on the scale. Many EC or ppm readers can automatically do this conversion.
The lower the ppm, the less nutrient-dense your solution.
When your cannabis plant is at the seedlings or early sprouts, stick to 100 to 250 ppm. When it grows into the early vegetative stage, ensure it reads 300 to 400 ppm.
The full vegetative stage of the cannabis plant requires a ppm of 450 to 700, while the early flowering stage requires 750 to 950 ppm.
As your plant grows into the peak flowering and ripening stage, ensure the nutrient scale reading goes up to 1,000 to 1,600.
Quick Tip:
- Always check what scale your nutrients are based on before mixing your nutrient solution.
Managing the Grow Environment
Growing a cannabis plant with hydroponics is different in many ways from growing in a soil garden.
Even after setting up your system correctly and selecting the right strain, you’ll need to pay close attention to temperature and humidity control, light management, and airflow ventilation throughout the plant’s entire growth cycle.
Temperature and humidity control
Cannabis plants grow best in temperatures between 70 and 85 degrees Fahrenheit. Make sure your grow room stays within this temperature range.
You’ll also need to monitor the humidity in your grow room. A dehumidifier can regulate the RH levels.
While the optimal relative humidity (RH) levels also depend on the strain you’re growing, it’s best to keep it at 60-80% during the seedling stage, 55-70% during the vegetative stage, 40-50% when it’s flowering, and 30-40% RH at the late bud stage.
Light Management
LED lights are a great choice for hydroponic growing because they provide lots of light while using little electricity. Many hydroponic systems and kits already have LED lights, so they’re a good starting point.
If your system doesn’t include LED lights, you can buy them separately and add them yourself. The intensity of the light and the distance are also essential factors to consider. The chart below can serve as a general guide:
Airflow and Ventilation
As you grow in your hydroponic setup, you want to prevent mould, pests, and stagnant air. This is where proper airflow and ventilation come in. You will need the following to ventilate your grow space properly.
- Extractor fan: This fan removes stale air from your growing space.
- Carbon filter: This filter cleans the air by removing contaminants.
- Oscillating fans: These fans help air circulate your grow room, improving airflow.
Many indoor growers use grow tents, often with vents for easy ventilation setup. Here’s how to set up an exhaust system in your grow tent:
Step 1: Put in your carbon filter and exhaust fan first. It’s easier to set up ventilation before you install your grow lights.
Step 2: After installing your lights, filter, and fan, connect them using ducting. Use ducting clamps to secure everything and some duct tape to fix any tears.
Step 3: Use ducting to direct air from your fan to a window or exit point.
Quick Tip:
- The ducting path should be short and straight so that it works efficiently.
FAQs
What is the Best Hydroponic Setup for Beginners?
The best hydroponic setup for anyone trying this cultivation approach for the first time is the Deep Water Culture (DWC). It doesn’t involve too many steps to build. A beginner can find it easy to monitor and maintain this setup.
How do I prevent root rot in hydroponic growing?
The best way to prevent root rot, especially when using the DWC hydroponic setup, is to have optimal temperature control.
Maintain water temperatures between 65 and 73 degrees Fahrenheit. This reduces the fungus’s ability to grow and prevents other pathogens, like Pythium, from causing root decay.
Also, consider adding hydrogen to your nutrient solution. Hydrogen peroxide can help oxygenate and separate roots to prevent root rot.
How Much Does It Cost to Set Up a Hydroponic Grow?
The average cost to set up a hydroponic system ranges from as low as $300 to $1000 and more, depending on the magnitude of your cultivation. Large-scale greenhouses can cost as much as $1 million.
Generally, the expenses will cover purchasing seeds, growing medium, nutrients, pH testing kits, and other operational costs.
How Often Should I Change the Water in My Hydro System?
Generally, you should replace the water every two to three weeks. Depending on the hydroponic system, you may need to add water daily.
Final Thoughts
Growing weed plants hydroponically may sound hard at first. But once you buy high-yielding feminised seeds, choose a comfortable setup, follow the best practices and exercise patience, the reward is worth the initial effort.
If it’s your first time trying hydroponics, we recommend starting with a small grow area and just a few plants.
As with most things, it will take experience for you to get better. But we hope this guide gives you a good start.