How to Create the Best Environment for your Cannabis Hydroponics Setup

Two hydroponic cannabis plants
September 26, 2020

After spending considerable time determining the hydro system you are going to set up, you must be feeling excited. Before you start shopping or begin growing, take a moment to learn how to create the best environment for the cannabis plants to thrive. Implement these recommendations, and you can expect a high yield of the most aromatic and potent buds.

In creating the perfect growing circumstances for hydro, there are two things you should think about – nutrient solution and atmospheric conditions.

Nutrient Solution

Your plants will need sustenance to grow. Apart from choosing the best nutrients formulated explicitly for hydroponics, there are other considerations. The source of water is one, and its acidity/basicity after mixing in the nutrients. Furthermore, you should also know which nutrient mix to use and how much to provide. Lastly, the roots should also have an adequate supply of oxygen.

What Hydro Nutrients Should You Use for Cannabis?

Let’s get one thing out of the way – soil and soilless mediums are not the same. The water in a hydroponic system may or may not contain trace minerals, depending on the source. Because of that, you should only use liquid nutrients formulated for hydro use.

Difference Between Nutrients for Hydro and Soil

Most, if not all, reputable brands would have products for soil and hydro. In that regard, you would not have trouble sourcing for a suitable nutrient formulation. Before continuing, you should know how they differ to understand why nutrients for soil should never be used.

Micronutrients. Soil mediums contain trace amounts. In hydro, most water people use has zero, which is why hydro nutrients should have micronutrients.

Nitrogen. Hydro nutrients have higher concentrations of this essential macronutrient, unlike in soil where it is already found in abundance.

Phosphorus. Hydro nutrients contain less concentration of this mineral because they are better absorbed. On the contrary, soil formulas have more to compensate for “losses” due to microbes and colloidal particles.

Chelated Minerals. One reason for the explosive growth of plants is being fed specially treated minerals, making them much more soluble and a little less affected by fluctuating pH levels.

Organic. Soil mediums contain microbes that break down organic matters. Your reservoir does not have these microorganisms, so providing them to plants in a hydro setup is a bad idea.

Reasons to Use Nutrients Formulated for Hydro

There are, of course, plenty of options. Apart from numerous manufacturers, each of them may also have more than one line of base hydroponic nutrients. You can narrow down the list of suitable products by setting these criteria:

  • Nutrients are explicitly made for use in a hydroponic system.
  • Does not contain organic matter. If it did, those matters would mess up the reservoir, causing bacterial growth, root problems, and even clogged pipes and drains.
  • Minerals are chelated. By wrapping nutrients inside an organic molecule, they become less affected by pH. As a result, they remain soluble in a broader pH range. Even if the pH tips above and below the optimal levels, the plants can still absorb them.
  • Have micronutrients to make up for what should be available in soil mediums.
  • Have optimal NPK ratios for both the vegetative and flowering stages.

Optimal NPK Ratios for Cannabis in Hydroponic Nutrients

Nitrogen (N), Phosphorus (P), and Potassium (K) are the three essential macronutrients cannabis plants need, much more so than others. Their ratio changes depending on the growth stage.

Growth Stage N P K
Vegetative High Medium to High High
Flowering Low High High

One thing you should know about hydro nutrients is that they usually come as a trio. It is not one kind of nutrient mix per life stage. Far from that, they are used at the same time in varying ratios and concentrations. The reputable brands would have a feed chart to guide you along.

Can You Use Any Water for Hydroponics?

Pure water has a neutral pH level. Any other substance – minerals, chemicals, and other impurities – can change its characteristics. Because that is what you use most in a hydroponics system, it follows that you should also know precisely what it contains – and that depends on the source.

Tap. In cities and other urbanized areas, the water supply comes from a public utility company. It contains chemicals – usually chlorine – to kill bacterias and other microbes but also changes the pH.

Deep Well. In rural areas, it is not uncommon for people to get water from underground wells. These waters usually would contain minerals, especially calcium. The high mineral content is why you see a crusty white buildup around fixtures and drains, which is why they could also clog pipes and tubes in a hydro system.

Filtered. For convenience, you are better off using filtered water. It can be carbon-based filters or reverse osmosis systems. The idea is to remove all the minerals and impurities. Starting with pure water makes it so much easier to give the plants exactly what they need with regards to ratio and concentration.

Note: Concerning water, be sure to read the following sections on pH and solutes.

What Is the Optimal Cannabis Hydro pH Range?

The pH level affects minerals differently, making them either more or less soluble for the plants. In hydro, the “common ground,” or the optimal range in which the plants can absorb all the needed minerals sit between 5.8 and 6.2.

Using chelated hydro liquid minerals, as mentioned earlier, broadens the optimal range. At 5.5 to 5.8 or 6.3 to 6.5, although not ideal, is still satisfactory, and your plants should not experience any trouble at all.

Once you go off the charts, so to speak, then you need to act quickly, making adjustments to bring the pH back to the optimal range.

pH Level Fluctuation

Compared to soil mediums, the pH level in hydro is more volatile and thus fluctuates more often. This “instability” is why you need to monitor the pH frequently – at once a day. Once out of range – too low or too high – plant growth slows down as they starve.

You could say that the frequent measuring and adjusting of pH levels when growing cannabis in hydroponics is more work and hassle. But it is also a part of the reason why the plants thrive.

Consider this.

Calcium and magnesium, for example, are more soluble at pH 6.0 and above. Other nutrients such as manganese, on the contrary, are better absorbed in slightly lower pH.

Because of the different solubility of minerals in varying pH levels, there is no single pH that is best for cannabis – and any other plants for that matter. That is why you maintain the optimal range (as opposed to a fixed level), allowing fluctuations within that small range. It gives the plants a chance to absorb different minerals more efficiently.

Measuring and Adjusting pH

You do not want to see leaves turning brown or yellow. But that can happen when the pH level is off the scale. Consequently, the plants start wilting, and growth comes to a halt. You can prevent this problem by arming yourself with a measuring tool and knowing how to make adjustments.

In this day and age, the most practical tool is a portable digital pH meter. It is a cheap device widely available and quite effective at measuring the nutrient solution’s pH level. Once you have it in your hands, follow the manufacturer’s instructions on calibrating. For recirculating systems, dip the probe into the reservoir, and moments later, the pH is displayed on the LCD. And for drain-to-waste, the pH of the media changes as the nutrient solution passes through and drains. Measure the leachate – the water that flows out at the base of the media.

You can use commercial “pH up” and “pH down” solutions, but make sure they are formulated for hydroponics. Although more costly, you may opt for an automatic pH controller system, applicable for recirculating water systems. It takes away the hassle of daily monitoring and routine adjustments by doing these tasks for you.

Why and How Do You Use an EC/TDS Meter?

You need a way to know the concentration of nutrients in the reservoir. Otherwise, it becomes almost impossible to adjust the dosage throughout the life cycle of the plants. A digital meter that can measure electrical conductivity (EC) and total dissolved solids (TDS) serves that purpose.

Electrical Conductivity

EC is a measure of the water’s ability to conduct an electrical charge. Pure water, which does not contain any other substance, cannot conduct electricity – making it an excellent electrical insulator.

Once there are substances that dissolve into water, it stops being an insulator. Salts, in particular, are ionic compounds that comprise positively charged ions called cations and negatively charged ions called anions.

Cations (usually from metal) and anions (from a non-metal) negate each other, leaving the solution electrically neutral. Their presence, though, even in tiny amounts, makes the solution able to conduct an electrical charge.

The higher the concentration of salts, the better the solution can conduct electricity.

Measuring EC is an excellent way of determining the solution’s salinity. However, it does not tell you the ion composition. Not all essential nutrients affect the EC.

Unit of Measurement:

  • mS/cm (millisiemens/cm) or μS/cm (microsiemens/cm)
  • 1 mS/cm = 1,000 μS/cm

Total Dissolved Solids

TDS is a measure of all organic and inorganic substances (molecular, ionized or micro-granular suspended) in a solution.

There are two ways to measure TDS:

Gravimetric. This method is accurate but entails heating and evaporating the solution before weighing the remaining residue. One caveat is that it works only with inorganic matters. Organic materials, on the other hand, could be destroyed when heated.

Conduction. The gravimetric method requires specialized equipment and is not suitable for growing cannabis in the house. Instead, a digital TDS meter is used. It works by measuring the EC of dissolved salts and uses a conversion factor to determine TDS (indicated as parts per million or ppm).

Conversion Factor

Digital TDS meters that you can buy online or in horticultural supply stores have a predetermined conversion factor of 0.5 or 0.7. Ideally, it should be adjustable so that you could match it with the nutrient mixture. Such a high degree of precision, however, is not required for hydroponics.

A digital TDS meter, as some people like to say, is an EC meter in disguise. First, it takes a reading of the dissolved salts. Then it multiplies the EC by the pre-set conversion factor to account for other substances in the solution.

For example:

EC: 2,000 μS/cm x 0.7 = 1,400 ppm or EC: 2,000 μS/cm x 0.5 = 1,000 ppm

As you can see, the figures vary. TDS is only an estimate and requires you to calibrate the meter. Moreover, using different brands may even give you different results.

Use EC or TDS?

Most people recommend using EC. For one, it does not require calibration. You can use any EC meter, and the results will be the same, possibly with some slight difference that is negligible. You should also look into the manufacturer’s feeding schedule of hydro nutrients to see their recommendations on measuring EC or TDS.

In the above example, FoxFarm, one of the famous brands used by cannabis growers, has recommended EC and TDS measurements. Since EC is much more convenient to use, then you can base your nutrient mixture on that.

How Do You Provide Oxygen to Cannabis Roots?

In hydroponic systems, such as deep water culture, aerating the reservoir is through an air pump and airstones. The bubbles that form create ripples and oxygen is taken from the surface. Considering that the atmosphere comprises 21% oxygen, it works but mostly to replenish those absorbed by the plants.

Dissolved oxygen (DO) in the nutrient solution plays several essential roles. For one, it prevents the growth of anaerobic bacteria that cause root rot. Remember how you were told not to drink stale water? That is because its oxygen is already depleted, leading to the growth of anaerobic bacteria, which may cause diarrhea, cramps, nausea, headaches, or other symptoms.

A high concentration of DO also promotes the rapid growth of roots and denser of root hairs. Furthermore, it also enhances the ability of the plants to absorb nutrients.

A simple method of increasing molecular oxygen in the nutrient solution is “fluming” (or “flooming”). It entails using a water chiller and a recirculating pump to cool down water while also creating surface turbulence. Not only is it more effective than airstones, but it is much quieter too.

The temperature of the nutrient solution also affects the capacity of water to hold dissolved oxygen. Generally, the lower it is, the more DO water can hold. But you should ensure that the temp stays within 64°F (18°C) to 72°F (22°C). Too cold and the plants’ metabolic rate slows down, while too hot and root rot becomes a problem.

Because you only have approximately four degrees for adjustments, its repercussions are not significant enough for you to lose sleep.

Atmospheric Conditions

On the surface, above the nutrient solution, you should also provide the perfect environment for optimal growth. The choice of which type of grow light to use has a ramification on growth. More light, as many growers believe, equates to high yields. But be mindful of the room temperature and humidity level. You should also ensure adequate ventilation and air circulation.

What Kind of Grow Lamps Should You Use?

After already investing in a hydro system, it does not make sense to skimp on grow lights, choosing the best grow lights to suit your needs is an important first step. There is no reason for you to spend a fortune as there are numerous affordable options. For you to maximize the returns, the better choices would be the tried and tested HID (MH + HPS) or full-spectrum LED lights. As for yields, the high-end models can compete with HID.


High-intensity discharge (HID) lamps are the gold standard of lighting for cannabis plants. They are costly as you would also need other equipment to use this type of light.

MH Bulb. Metal halide is used during the vegetative period. The blue spectrum promotes the growth of stems and leaves.

HPS Bulb. High-pressure sodium is yellowish and used during the flowering stage. Compared to any other type of lighting, this one helps the plants produce the highest yields.

HID lights, while powerful, also emit plenty of heat. For that reason, you need to install vent fans that expel warm air while drawing in fresh, cool air. Furthermore, you also need an electronic ballast to power the bulbs.

Despite the additional costs, you can expect to harvest around 0.5 to 1 gram per watt. For example, a 600w HPS lamp should produce 300 grams (10.6 ounces) to 600 grams (21 ounces) of buds.


LED grow lights have come of age. They are better than ever and run cooler than HID lamps. More importantly, they can provide all the color spectrum needed by cannabis plants to thrive and cost far less. Most of the horticultural LED lights have a built-in fan to keep them cool. Plus, they are quite easy to install.

At What Temperature Range Does Cannabis Thrive?

Too hot or too cold, and your plants would be impacted negatively. Moreover, it also affects the humidity, which introduces more problems. On the other hand, if you keep it in the optimal range, that is already one of the keys to healthy plants and maximum yields.

A cold temperature lower than 60°F (15°C) slows down growth. Freezing temperatures are worse as the shock could kill the plants. Unless rectified, you may also have to deal with molds (especially when the moisture level is high).

On the flip side, excessively high temperatures can also stunt growth. Even if the plants were to survive, the buds produced are likely loose or airy and not as potent or aromatic as they should be in ideal conditions. You might encounter pests such as spider mites above 80°F (26°C).

The water transpiration increases – it is the plants’ defense mechanism against heat. And that may lead to nutrient burn or root rot. The nutrient solution’s capacity to hold dissolved oxygen also diminishes, which may lead to wilting.

Invest in a few thermometers, and place them strategically in the grow room to make sure there are no areas that are too hot/cold.

What Is the Best Humidity Level for Cannabis in Hydro?

Warm air holds more moisture, cold air holds less. And that is how temperature affects the humidity levels. A hydrometer comes in handy, letting you take a reading. If need be, you can make the necessary adjustments.

Here are the recommended humidity levels across the life stages.

Clone Vegetative Flowering Final 2 Weeks
70% 40% to 60% 40% to 50% 40% to 45%

When you make adjustments, do so gradually in increments of 5% per week to gently acclimate the plants. Abrupt changes can cause excessive stress, which may lead to stunted growth.

How Do You Circulate Air in the Grow Room?

By controlling the temperature inside the grow room – using exhaust and vent fans to expel hot air as fresh air comes in – is already a good start. But that may not be necessarily enough. Remember that there is a reservoir and running nutrient solution, and that adds to the moisture. Moreover, the warmer it is, the higher the capacity of air to hold moisture.

A humid environment can cause several issues – heat stress, root problems, and bud rots. It could also attract white powdery mildew, fungus gnats, and spider mites.

Having adequate air circulation prevents those problems – and it is as simple as adding an oscillating fan in the grow room. Instead of using a single, medium-sized fan, though, you are better off using the two or more small ones that are strategically placed.

Remember that there are two layers in the grow room – above and beneath the canopy. The temperature and humidity above may be controlled, but not necessarily beneath, where moisture build-up may occur.

In installing fans, place them so that they could cast a slight breeze on the stems and leaves. Make sure that air circulates on the upper canopy and the lower branches. Doing so not only helps make managing temperature and humidity levels easier. The slight movements are also a form of exercise, strengthening the stems and branches.

A Little Bit Here and There for the Perfect Grow Room Environment

There is no one way to create the best environment for cannabis plants in indoor hydroponics grow rooms. Instead, it is tweaking several factors that affect growing conditions.

Briefly, here’s a list of things you should think about and optimize:

Concerning nutrients, be sure to use formulations for hydro. Make sure to use water that is free of contaminants and chemicals. Follow the recommended mix and feeding schedule but gently start with conservative concentrations before bringing them up gradually. You should monitor the pH level, EC (or TDS), and also keep the nutrient solution at ideal temp.

Atmospheric conditions also play a huge role in growth. The plants definitely need a source of light for photosynthesis. You can’t go wrong picking between MH+HPS or full-spectrum LED grow lights. Exercise due diligence monitoring the temperature and moisture level. Any deviation towards too high or too low is going to cause issues. Lastly, ensure that there is adequate air circulation.

On the surface, thinking about all these factors can seem overwhelming. The best thing to do is to compartmentalize. Think through before going about the task of caring for the plants – one at a time. In time, you may have to change a step, sequence, or workflow. That is okay. Before you realize it, tweaking the parameters to provide the best conditions for your plants has become second nature.

If you have any further queries relating to hydroponics, then head over to the hydroponics section on the Homegrown Forum and start sharing and receiving knowledge relating to hydroponics.