The term ‘hydroponics’ is a Latin term that translates to ‘water working.’ In terms of growing weed, it relates to producing the plants in highly oxygenated water enriched with additional nutrients. In basic terms, hydroponic marijuana is cannabis that is grown without soil. There are several ways to grow marijuana hydroponically. You can suspend the roots of your plants in Rockwool, clay pellets, water, coco peat, sand, or gravel.
Regardless of what you use as a growing medium instead of soil, you have to apply a nutrient-laden solution to the roots. The water that isn’t absorbed by the roots gets recycled through the system for later absorption.
This extremely detailed guide looks at:
- What hydroponic cannabis is
- How to set up your system
- The different types of hydroponics systems
- The best cannabis strains for this process
- Tips on cultivating hydroponic marijuana
- Common hydroponics problems and how to solve them
Simply put, you will find practically everything you need to know about hydroponic cannabis in this article.
What Is Hydroponic Cannabis?
Hydroponic marijuana refers to a means of growing using a soilless system. In other words, you cultivate plants using an inert growing medium and nutrient-rich solutions. Previously, the assumption was that hydroponic set-ups were complicated and expensive affairs designed solely for commercial growth.
However, in reality, you can engage in marijuana growing with hydroponics using something as simple as a few pots containing the inert medium. By all means, you can opt for a more complicated option, but it requires significant set-up time and a ton of maintenance.
Growing cannabis hydroponically has become an increasingly popular method because of the issues associated with using soil. It is a much better option for indoor growers who face the following problems when growing marijuana ‘traditionally’ using soil:
- A constant need to monitor the pH of the soil
- Ascertaining the correct level of nutrients
- There is always a potential problem with pests
- You might not be able to recycle the soil you use
- You have to choose the best soil because its quality dictates the size and potency of your final product
With a hydroponics setup, you are responsible for providing the plant with all of its nutrients. If you get it wrong, your plants will die or produce a small and unsatisfying yield. On the plus side, a hydroponic system ensures that your marijuana plants’ roots easily find nutrients and don’t waste energy looking for them.
All hydroponic systems must provide oxygen, water, and a host of nutrients to marijuana plants. Nutrients include:
Nitrogen, Phosphorus, and Potassium are the essential nutrients, however. Most solutions contain 15% of each, also known as a 15-15-15 solution. If you grow weed in temperatures below 80 degrees Fahrenheit, you need higher amounts of nitrogen. Other possible solutions include 20-20-20 or 23-19-17.
During the flowering process, increase potassium level so that it comprises at least 20% of a solution. Be wary when fertilizing the plants because too much kills them while too little slows growth. When your reservoir’s water level gets low, add three-day-old tap water. It is also good to change the nutrient solution every two weeks and use hot water to clean out all the equipment you use, especially the pumps and reservoir.
Setting up Your Hydroponic Cannabis Growing System
There are several hydroponic gardening systems to choose from, and all of them are suitable for growing cannabis indoors. Regardless of the method you use, the overall tactic involves using a reservoir containing the nutrient solution. You then place it beneath a growing tray. This tray holds the inert growth medium of your choice, such as sand, gravel, or Rockwool.
Hydroponic cannabis involves growing the plant in the medium, where it develops a set of roots and a stem. The roots grow through the medium and into the nutrients. You use a small pump with a timer to fill the bottom layer with the nutrient solution. After an allotted period where the plants are fed and watered, the timer shuts off the pump, and the solution drains back into the reservoir.
The hanging root structure of the plants means they are exposed to air constantly, and the result is a crop of flourishing plants. Your cannabis plants can use their energy for the sole purpose of maximizing growth. With soil, they waste energy trying to find air, food, and water. This is why marijuana grows so spectacularly in a well-designed hydroponics garden.
You should find the so-called ‘plug and play’ hydroponic systems that provide everything you need to get started. Even so, here is an essential list of things you’ll need for a starter system:
- One large (3 – 5 gallon) bucket per plant
- A water pump
- An air pump
- A reservoir tank
- An air stone
- A grow table
- A growing medium such as Rockwool or clay pellets
- Plastic tubing
- A drip line and up to two drip line emitters for each plant
There are many indoor hydroponic systems to choose from, but we will only focus on the best known.
Types of Hydroponic Systems
Deep Water Culture (DWC)
This is one of the most straightforward hydroponic systems to use, making it ideal for beginner growers. All you have to do is put the plants in separate containers and place each one in a grow tray that gets suspended in water. Your water tank will have an air pump that ensures the water remains oxygenated. Then you add nutrients to the water to feed the roots.
Although you submerge the roots in water, the oxygenated air pumps ensure they receive ample oxygen.
This is a popular commercial option because it saves a lot of water. You need to place small droppers beside the plant’s roots, which are in pots containing the growing medium. Little drops of this nutrient system drip out regularly and feed the plant. It offers a low level of evaporation, and, as it is silent, it is perfect for a covert operation to keep your grow area protected from thieves.
This is a unique method because you don’t use a growing medium. Most growers tend to use a tiny amount to root a cutting or germinate the seed, however. The roots of the marijuana plant are suspended mid-air inside a chamber kept at 100% humidity. You must use a fine spray filled with nutrients.
This form of feeding enables the roots to absorb large amounts of oxygen. As a result, the plant can grow up to 10 times faster than it would in soil, with practically no water loss through evaporation. If you use this method, be wary of clogged misting valves as they could prevent moisture from getting to the roots. This will kill your plants.
Ebb & Flow
This is different from several hydroponics systems because it does not involve the continuous submersion of the roots in water. It works similarly to an ocean tide, as it fills a tray with oxygenated water and treats the plants and growing medium. When it is full, the pump switches off, and the solution drains into the reservoir. It stays there until you are ready to flood the garden again.
Nutrient Film Technique (NFT)
NFT is a complex system and involves pumping your water solution from the reservoir to your planting tube. It is common to use large PVC tubing angled at a slight decline. This tactic ensures that when the water drains down the pipe, it passes by the roots of all marijuana plants before it gets recycled in the container.
One of the most significant problems with this system is that the water solution could fail to leave the tube, stagnate in the channel, and kill your plants. This is why you need to make sure the tube is cut at a steep enough angle to allow for easy passage of the water.
This is another easy-to-use system. It works like a DWC system insofar as it uses a material such as a length of rope through a PVC tube. You pull the solution up the line and place it in the tray. With the wick system, you don’t need to bring the water to the plants. It may not result in plants that grow as quickly as they would with more complex systems. However, it is the ideal way to learn hydroponics through practice.
What Are the Most Common Hydroponics Growing Mediums?
While there is a wide range of growing mediums, five of them stand out. Please note that each option varies in its ability to retain water and allow oxygen in.
Although they are light enough to work with efficiently, clay pellets are still sturdy enough to support marijuana plants, and they are reusable! They wick moisture up to the roots and enable oxygen to flow through due to the size.
This medium is popular because it retains moisture exceptionally well. It consists of thin rock fibers developed by heating rock to very high temperatures and spinning it into tiny threads. If you purchase Rockwool as a hydroponic growing medium, soak it in a solution with a pH of 5.5 for up to 12 hours. Make sure its pH is between 5.5 and 6 before use.
This is a more environmentally-friendly option than Rockwool because these fibers come from waste products. As well as retaining moisture and allowing in more oxygen than Rockwool, coconut fibers contain hormones that keep infection and disease at bay.
This porous white substance retains and wicks moisture exceptionally well. Generally speaking, you should purchase large chunks rather than small granules. The surface of each perlite particle is covered with tiny cavities. The result is a vast surface area that holds nutrients and moisture. It is a sterile substance, so there is no danger of pests, insects, or diseases.
This is another crushed volcanic rock medium like perlite and is also known for its terrific drainage. Although it is sterile, vermiculite is not generally used as a growing medium by itself, with growers electing to mix it with perlite. If you decide to use it, ask the seller where they got it from. For example, vermiculite that comes from Africa is very alkaline, with a pH of up to 9.0.
While hydroponics has many advantages, there are more than a few downsides. Let’s explore both sides of the coin next.
The Pros & Cons of Hydroponics
- It allows for higher yields from smaller growth areas.
- Almost total control over the growing process, which typically means better quality cannabis.
- Weed grown using hydroponics matures faster, and experienced growers can complete six crops in a single year.
- As there is no soil involved, you don’t have to worry about a myriad of pests, which means no need to use pesticides.
- Assuming you monitor everything correctly, there is a lower risk of water stress than with crops grown in soil.
- As you have full control, you can even tailor feeding schedules to the needs of a specific plant.
- You won’t get your hands on a decent quality system for mere pennies. If you are a recreational grower, this kind of system is probably more trouble than it’s worth financially.
- Although you reduce exposure to disease, there is a unique danger associated with water-borne plant diseases. They spread incredibly quickly and are extremely difficult to remove.
- Barring the Wick and DWC systems, it is a complicated process that requires knowledge and patience.
Best Hydro Weed Strain
There are hundreds of cannabis strains widely available online. However, we feel that the following five provide a nice mixture between being relatively easy to cultivate and providing a high yield:
27 ounces per square meter
29 ounces per square meter
32 ounces per square meter
28 ounces per square meter
52 ounces per square meter
Tips for Growing Your Hydroponic Cannabis
It should go without saying that using a hydroponic growth system is very different from traditional methods of growing weed indoors. As a result, there are a few things to consider when trying to grow marijuana plants in a hydroponic garden system.
It is impossible to overstate the importance of using clean equipment at the very beginning. All tanks, reservoirs, filters, pipes, and other equipment must be sterile to prevent the development and spread of bacteria. Although hydroponic systems are less susceptible to diseases, they will run rampant if left unattended. It is a good idea to have multiple bottles of hydrogen peroxide and isopropyl alcohol on hand to disinfect your equipment.
Make sure that pH-neutral water at 7.0 is circulating through your hydroponics system. You can create a reverse osmosis (RO) method to generate and provide pH-neutral water. Alternatively, purchase distilled water until you’re able to develop the RO system.
It is best if the water flowing through your system is at a temperature of 65 degrees Fahrenheit. This is the ideal temperature for nutrient absorption, and it also prevents algae buildup. As for your growing room’s temperature, keep it at 75 degrees Fahrenheit to begin with.
When growing cannabis indoors, maintaining the right humidity levels is a constant challenge. You have to begin with relatively high humidity and dial it down as your plants grow. As seedlings and in the vegetative state, keep the moisture in the 60-70% range. Reduce by up to 5% weekly until it is at around 40% during the blooming stage. You may need to purchase a humidifier and a dehumidifier to achieve these targets.
There is no ‘right’ lighting set-up, only the best one for your grow space and budget. For example, if you have a large room with excellent ventilation and airflow, you can purchase High-Intensity Discharge (HID) lights.
If you have a smaller growing room, try Light Emitting Diode (LED) fixtures or Compact Fluorescent Lights (CFLs) if you have a more modest budget. Overall, choose lighting that produces a sufficient amount of light between 400 and 700 nanometers.
Good airflow helps keep temperatures at the right level. Invest in a few fans and place them strategically in your growing room.
Regardless of whether this is your first grow or you’re a veteran, it is essential to keep detailed records of your crop’s growth. It is not unusual for novices to enjoy spectacular success, only to realize that they failed to record any data. Important notes include pH levels, planting dates, EC measurements, temperature, and humidity.
While growing hydroponic cannabis is an exciting option with many possibilities, there are also obstacles to overcome.
5 Hydroponics Problems and How to Solve Them
When you cultivate hydroponic marijuana, you are in control, so your crop requires constant attention. A hydroponic system exposes the roots to severe damage if you run out of water or suffer a pump failure. Even a slight change in pH can cause immense issues! While hydroponic marijuana is less likely to have issues with disease, illnesses run rampant once they ‘get in.’
If you are new to growing cannabis using a hydroponic system, you will likely make a mistake or two. Failure to rectify the situation can have devastating consequences. Fortunately, there are several errors that novices make over and over again. Even better, it is possible to ‘fix’ things before they get out of hand. In this guide, we outline five common hydroponics problems and how to solve them.
1 – Choosing a Suboptimal Hydroponic System for Your Grow Space
It is possible to create a hydroponic system in a relatively small grow space. Of the options we outlined earlier, NFT is for advanced growers. The drip system is for intermediates, and the others are suitable for beginners. Before choosing a hydroponic system, consider your experience, skill level, finances, and space. If you don’t think about efficiency and workflow, you end up with a farm that:
- Is difficult to harvest
- Doesn’t use space efficiently
- Isn’t good at pest control
- Involves a lot of transplanting and maintenance
- Doesn’t enable you to access crucial components
Growers who have a system in their basement often make an elementary mistake. They place their nutrient reservoir at the side of the grow table. When they need to ‘flush,’ they find that a bucket is the only way to drain their tank.
The Fix – Map out a Plan
Those with a low budget and minimal space should lean towards the Wick System. It is arguably the easiest to implement. The more parts in your cannabis garden, the higher the risk of problems. Your grow tray gets its nutrients from a wick made of yarn or cotton, which brings the nutrients to the roots.
When using the Wick System, choose smaller plants because larger ones require a lot of water. They could also potentially use the nutrient solution faster than you can supply it. Bear in mind that the Wick System is also the least efficient and may produce the smallest yield. However, you are less likely to encounter problems.
As a general rule, make sure you consider all variables. This includes growing needs like light and water and user needs such as convenience and access. If you are a beginner, there is no need to shoot for the stars. Keep things simple at first, understand the hydroponics process, and learn. Meanwhile, enjoy the yield from your first successful operation!
2 – Lack of Attention to pH Levels
This is an issue when initially transitioning from soil to a different growing medium. You are so used to soil remaining in its pH zone that you forget its importance. Remember that the ‘ideal’ pH in a hydroponics system is between 5.5 and 6.5. This is slightly lower than in soil when the right level is between 6.0 and 7.0.
It’s easy to underestimate the difference a few pH points make. The pH scale is logarithmic to the base 10. Therefore, water at a pH of 5.5 is ten times more acidic than at 6.5.
pH in a hydroponics system should be between 5.5 and 6.5. This is lower than the optimum for soil.
The pH of a growing medium has a profound effect on its nutrient uptake. If you grow marijuana outside the right range, your plants will experience ‘nutrient lockout.’ From there, it doesn’t take long for cannabis nutrient deficiencies to manifest. However, it isn’t merely a case of allowing the pH to remain at a certain point. It is necessary to enable fluctuations within the specific range.
Nutrients such as calcium and magnesium are absorbed at a pH of above 6.0 in general. However, the likes of manganese and phosphorus prefer a slightly lower pH. In a hydroponics system, you are solely responsible for adding nutrients directly to the root zone via water. As a result, significant fluctuations in pH are more likely than in soil. It doesn’t take long for it to become a problem.
The Fix – Monitor, Test & Adjust
The process of testing your nutrient solution or water for pH levels isn’t nearly as complicated as it seems. You can easily purchase a pH measurement kit with drops or a digital pH meter online. Ensure you test the pH after every occasion when you add nutrients as they change your water’s pH level. Wait a few minutes and test a sample from the water reservoir.
If the pH level is out of the optimal range, there are special ‘pH +’ and ‘pH – ‘products on the market. If you are using tap water in your reservoir, the pH will likely be above 6.5 as the water is close to 7.0. It usually only takes 1-2ml of the solution per gallon of water to make a positive difference. Stir the product into the water and wait for up to 30 minutes to test the pH again. Repeat the process if the pH remains outside the 5.5 to 6.5 range.
Citric acid and white vinegar can lower the pH. Baking soda is commonly used to increase pH. You can use these items in a pinch, but they are only short-term fixes at best.
3 – Incorrect or Excessive Nutrients
Don’t make the mistake of thinking the only thing you need is a good water to solution ratio. Your crop requires different N-P-K ratios and other minerals at varying stages. For example, plants in the vegetative stage require a high degree of nitrogen. The focus shifts to potassium and phosphorus in the blooming stage.
Some growers buy a sack of fertilizer from their local store and use it in their hydroponic system. ‘Regular’ fertilizer could clog tubes and drains and may not dilute thoroughly. Also, you can cause as many issues overfeeding as you do from underfeeding. It is far too easy to produce a nutrient burn, a process that hinders yield.
The Fix – Know Thy Nutrients
It isn’t all about N-P-K. You must learn to add sufficient levels of micronutrients such as magnesium, calcium, sulfur, and manganese, for example. However, Nitrogen, Phosphorus, and Potassium are three of the six macronutrients a plant needs to live. The other three, oxygen, hydrogen, and carbon, are supplied by air and water.
Rather than buying traditional fertilizer, invest in specific hydroponics nutrient packages. On the front, you should see the N-P-K content. If the product says 7-5-5, it means 7 parts nitrogen to 5 parts potassium to 5 parts phosphorus. Though there are no specific ratios, experienced growers suggest the following:
Plant Growing Stage
Suitable N-P-K Ratio
Early Vegetative Stage
Advanced Vegetative Stage
The transition from Vegetative to Flowering Stage
Early Flowering Stage
Full Flowering Stage
Final Flowering Stage
4 – Lighting Issues
If you skimp on lighting, you will never enjoy the results you crave. Too many growers believe it is a case of buying the strongest light possible, and to hell with the consequences!
In reality, marijuana plants require lighting at different spectrums according to their growth stage. They also need a specific intensity, and you must get the duration correct also. Most growers know what happens when their plants don’t get enough light. However, if the intensity is too high, you end up with short and stout plants.
In the beginning, most hydroponics growers used High-Intensity Discharge (HID) lights for growing. While HID lamps provide plenty of light, they also waste a ton of energy. Therefore, you need to invest in a high-quality ventilation system. HID lamps also require a ballast.
LED lighting has come to prominence in recent years. They provide a spectrum ideal for every growing stage and don’t require a ballast. Other lighting options include high-pressure sodium lights and Metal Halide (MH) lights. You can learn more in our best grow lights for indoor weed guide.
The Fix – Understand the Light Spectrum
All plants, including cannabis, use energy from light during the process of photosynthesis. The pigments in plants absorb specific wavelengths of light and reflect the rest. Though there are several essential pigments in the photosynthesis process, chlorophyll and carotenoid are the most critical.
You can customize LEDs to provide the precise colors your plants need at different stages. Make sure you purchase full-spectrum LED grow lights. By doing so, you ensure there’s no need to change the light when your plant changes growing stages. Ideally, your lights contain:
- White LEDs
- Far-Red LEDs
- Blue LEDs
- Red LEDs
It is also okay to include some green, IR, and UV LEDs. When you buy the right LED lighting, you’ll find they are configured for all growth stages. As a result, the colors are mixed, and you get the purple hue often associated with LEDs.
Bulbs are measured by color temperature in Kelvins. Above, you can see the different Kelvin measurements for varying forms of light. It is a little complex, but let’s simplify it by outlining ‘ballpark’ ranges for the various stages of growth:
- Seedlings & Clones: Bulbs at 5,000 Kelvins are useful. Fluorescent lights are a good option here.
- Vegetative Growth: Bulbs in the 5,000-7,000K range work well, and you can use Metal Halide lights.
- Flowering: Drop the range to 2,000-3,000K here. High-pressure sodium bulbs are a good option as they produce more red light.
Remember, LED lighting is an excellent option for every stage.
5 – Lack of Sanitation
Hydroponic systems are sterile environments. This means the entire grow room and not just the plants you are growing. The benefit is that your plants remain free from pests and diseases. However, if any harmful bacteria or parasites get into the system, they can spread rapidly and ruin your harvest.
The nutrient reservoir could have algae buildup, and the nutrient mix may cause an increase in salt content. In this case, the salt sticks to the pots and growing medium. Also, the warm and humid air in the room increases the risk of mold growth.
The Fix – More Attentive Gardening!
This is perhaps the most straightforward fix because it doesn’t require much technical skill. Instead, it involves diligence and a willingness to put in the time and effort needed. Your first goal is to ensure the floors are clean, dry, and sterilized at all times. Make sure you clean every single tool used in the system before use.
Whenever you flush your system, check nutrient reservoirs. It is the same situation with grow beds and piping. Ensure you rigorously check your pots and growing medium and clean them if you see a salt buildup. Also, remove plant waste as soon as you spot it. Any diseases caught by one plant will rapidly spread to others.
Sanitation is essential to healthy plants. Remove plant waste, diseased plants, and salt buildups as soon as possible.
We recommend investing in a high-quality fan to circulate air in the hydroponics room. This process also helps bring in fresh carbon dioxide and oxygen and keeps the temperature manageable.
Did you know that the amount of dissolved oxygen in your nutrient solution diminishes as the temperature increases? A lower level of oxygen damages root health. Excessively high temperatures also invite the presence of pathogens. Ideally, you will keep the nutrient solution at between 65- and 75-degrees Fahrenheit.
Final Thoughts on Hydroponic Marijuana
There is a lot to like about hydroponic marijuana. It enables you to grow a lot more per annum, and you only need a relatively small growing area to get started. It lets you grow high-quality cannabis in areas where you usually can’t grow in soil. There are fewer pests, and the overall quality of well-produced hydroponic weed is exceptional.
However, it is a tough skill to master, and the initial set-up costs are considerable. If you fail to keep the grow area wholly sanitized, your entire crop could succumb to diseases in double-quick time. It is not something you can learn overnight, but if you have the time, money, and patience, learning how to grow cannabis in this way could yield tremendous dividends.
However, we don’t recommend it for recreational growers, as it works best when cultivating large amounts.