2015 Hydro Report

Hydro Basics

Hydroponics is the art of growing plants without soil. A nutrient solution made up of water and plant foods is mixed in a reservoir and typically fed to the roots several times a day. The roots sit in an inert medium such as rockwool, perlite or grow rocks (also known as hydrocorn, puffed rock or expanded clay pellets). Some hydroponic systems, such as deep water culture (DWC), employ no medium at all; the roots simply dangle in an oxygenated nutrient solution and take up the liquid and foods as needed.

Automated hydroponic gardens are capable of producing pounds of pot efficiently.

Why Go Hydro?

The advantages of hydroponics over hand-watering plants in a soilless mix are many. Plants grow faster when their roots aren’t encumbered by thick, clumpy soil mix. With the ability to take in more oxygen through their roots, their explosive growth rates far exceed what can be accomplished in buckets full of dirt. Also, there is no bulky spent soil to get rid of, which can be advantageous in urban environments or warehouse grows, for which literally tons of soil are needed.

Another huge reason that people use hydroponics is that there’s much less chance of pest infestations. The lab-like conditions necessary for hydro don’t supply many places for pests to hide, thrive and reproduce. Also, many organic soil-based mediums and nutrients attract bugs with their smell of compost and rot. Introducing fish, seaweed or guanos will certainly bring more pest issues.

Hydro Systems

Ebb-and-flow trays periodically flood with nutrient solution and then drain back into reservoirs.

Nutrient Film Technique (NFT)

NFT uses round or squared tubes to deliver a constant flow of shallow nutrient solution. The plant roots sit in a trench and take up what they need, eventually forming a mat along the bottom of the tubes. It’s important to ensure that the water is well oxygenated when using NFT, because the roots dangle down into the solution.

Ebb-and-Flow or Flood-and-Drain

These systems use trays to contain plants in a growing medium. Nutrient solution is periodically pumped into the trays from a reservoir and then drains back to the reservoir for the next feeding cycle, allowing roots to take in plenty of oxygen between waterings without completely drying out.

Deep Water Culture (DWC)

In DWC systems, each plant gets its own bucket, typically 5 gallons or larger. The plants are secured individually in mesh pots cut into the top of the buckets, and the roots dangle down into an oxygenated nutrient solution. Sometimes the buckets are connected to a larger reservoir, but they can also operate as stand-alone systems.


Plants grown areoponically are fed a nutrient solution in the form of a mist aimed at the roots. The solution is fed via a pump through misters that bathe roots constantly, allowing them to absorb food while also taking in abundant amounts of oxygen. When aeroponic methods are properly dialed in, plants grow incredibly fast and big.

Nutrient Film Technique in action (L); DWC features individual buckets (C); Roots in an aeroponic system (R).

Aquaponics: Let Fish Do the Fertilizing

Aquaponics is an interesting method of soilless cultivation being used by urban-farming movements and some developing nations to produce crops—and fish—with just a fraction of the water needed in conventional farming.

Aquaponics is a combination of aquaculture and hydroponics in a closed system: The fish defecate in the water in one tank, which then gets regularly circulated through the hydroponic medium of the plants, whose roots extract the nutrients they need and clean the water for the fish. Beneficial bacteria play a central role in this system, helping turn ammonia-heavy fish waste into useful nitrates for your plants. All you have to do is sit back and feed the fish, and a “mature” system (i.e., one with enough working bacteria) will provide the nutrients necessary for the flourishing growth of many plants, cannabis included. And though there are quite a few predesigned aquaponic systems out there, the possibilities for experimentation are endless.

One thing to keep in mind, however, is that the fish provide only a source of nitrogen; the system on its own is deficient in iron, magnesium, sulfate, phosphorus and potassium. Iron DTPA chelate and magnesium sulfate can be added to the reservoir with no negative effects to the fish, but the amount of phosphorous or potassium desired for cannabis growth would be toxic to them.

So how have cannabis growers gotten around this? By using a system called dual root zoning (see the illustration), in which vegetative growth can match—and often surpass—even the growth seen using traditional hydroponic methods, while producing buds with the natural and earthy flavor of the best soil-grown organic. The grower adds just the right amount of a phosphorous-and-potassium-rich nutrient solution to the top soil layer, but the main water reservoir won’t be contaminated, because the soil mass absorbs it like a sponge. The system also uses a burlap flap that the plants’ roots can grow through to separate the layers of soil and hydrocorn. As a result, the root-ball can absorb all the micro- and macronutrients it needs without those nutes circulating through the system and poisoning the fish.

This does seem like a labor-intensive method, but in our rapidly changing and precarious world of water and energy shortages, resource-saving setups like this are just what the cannabis industry needs to be sustainable.

Hydro Mediums

Grow Rocks/Hydroton/Expanded Clay Pellets

Clay pellets are heated and then expand, forming what look like solid rocks that actually contain many crevices and air holes for oxygen to circulate. One advantage to pellets or grow rocks is that they can be reused many times, as long as they’re properly cleaned between cycles.


Rockwool is made from rock that is heated and spun into long fibers that resemble the insulation used between walls in buildings. It has the advantage of holding lots of water while also allowing air to reach the roots. Rockwool can be an irritant to the skin and lungs, so always get it wet before working with it.

Perlite and Vermiculite

Perlite and vermiculite are two forms of heated minerals that expand into small, porous pebbles. They are typically used to lighten soilless mixes, but they can also be used alone as a hydroponic medium. Both exhibit good water retention and also have “wicking” properties that draw the nutrient solution upwards.

Coir/Coco Peat

Made from the fibers on the exterior of a coconut shell, coco peat is a natural byproduct of the coconut industry. Many hydroponic growers enjoy using this medium over rockwool due to its sustainability as well as its water-retention capacity. However, this medium requires a unique and specific type of nutrient solution made especially for use with coco peat.

Hydroponics AND Sustainability

We live in an age of information. While this is undoubtedly a good thing, it can also mean that a lot of confusion and even flat-out misinformation gets propagated. The age-old hydro-versus-organics debate is a great example.

It would seem that only a fool would argue against organics. After all, that’s what people pay a premium for—whether at the grocery store or the dispensary, or even at your favorite grow-supply shop. For whatever reason, most of us tend to look at organics in a more positive light than synthetics. Fair enough—but there’s more to the story that we need to consider, and that concerns sustainability.

So let’s say that, being into tasty and clean-burning buds and having a sense of value for the earth and its ecosystems, you opt for a bag of peat-based organic growing mix and a couple bottles of your favorite organic nutrients. Feeling good about your choice? Wait a sec ….

First, almost all of the cost associated with peat- or even coir-based grow mix is actually related to shipping bulk materials. Peat is super-cheap at the source, because the producers simply tear it from the earth (even though it can take tens of thousands of years to accumulate naturally in a bog). So why does it cost so much? Because diesel fuel isn’t cheap. Those bulk materials travel long distances before they’re used in most regions.

A flood and drain table nourishes this luscious bud.

Now consider the carbon footprint: Not only have you added more carbon to our atmosphere from that petroleum-based global bulk shipping, but you also helped strip away a part of a living system here on our planet. And what were you planning to do with it once your harvest was done? “Throw it away and start a new crop with fresh bags” is the most common answer.

The same goes for “specialty” bottled organic fertilizers. While these can produce great yields and tasty medicine, they involve shipping a lot of water around and are manufactured, at least in part, with simple dry goods, most of which you can source yourself locally.

Here’s the deal with hydro: It can be more sustainable as well as more productive. But before we even go there, we need to get something else out of the way: Using hydroponic fertilizers or methods does not mean employing harmful PGRs (plant-growth regulators)—a common bit of misinformation. Synthetic nutrients are super-clean basic elements—some cleaner than others, with many being food- or even laboratory-grade. For example, one of the most common ingredients is monopotassium phosphate (MKP). This has been used as a common food additive for years and years, and all it consists of is potassium, hydrogen, phosphorous and oxygen—the same as you’ll find in a bottle of organic nutes, with one important exception: It’s in a stable form that your plants can take up right away for growth, and that won’t spoil or sour easily.

At the heart of hydro growing in its truest form is water culture (in Greek, hydroponics means “working with water”). In this method, there is no growing medium at all—or, at the most, a very small amount of a reusable material like grow rocks, which are used simply to anchor the larger plants. The roots of the crops are bare and kept from light and drafts—essentially, they have their own mini-climate that the grower can control.

In the super-oxygenated environment that’s optimal for roots, plants use nutrients more efficiently when they’re supplied in clean and available forms and in specialty hydroponic formulations. Also, oxygenated roots enable plants to grow bigger, faster and stronger with lower fertilizer levels. This means that 4-liter nutrient jug will last four times as long now—and that’s four times less fuel in the air than your bottle of organic nutes.

What about all that plastic? Professionally manufactured hydroponic systems are made from materials that last; they can be scrubbed clean with bleach and water and reused again—often on the same day as harvest, because prepping a hydro system is faster and easier, in most cases, than getting a soil-based system ready to grow again. If you use grow rocks, you don’t need many, because they too can be sterilized, rinsed clean and reused.

Oxygenated root zones promote healthy growth.

Hydroponics has many other advantages where sustainability is concerned. For example, systems and materials can be and are made from recycled plastics. A covered recirculating system uses considerably less water than traditional soil- or soilless-grown crops, because all of that water gets absorbed by roots—very little is lost to the air or as run-off. A well-managed or automated hydroponic reservoir doesn’t need to be dumped, either—with proper measurements and formulas, it can operate for the entire duration of the crop. And if your growroom gets too hot, you may not need that big energy-hungry air conditioner—a small one-quarter-horsepower water chiller cools the nutrient solution so that your crop can thrive in warmer temperatures, so long as the roots are kept at a perfect 68°F to 72°F.

There’s much more to the story than what we’ve touched on here, but it’s best for you to find out for yourself by dedicating a crop to hydro and experiencing the difference. While there’s no doubt about the great quality, heavy yields and fast growth rates that can be achieved using hydroponics, it appears that there are also important environmental benefits to this ancient and yet very modern growing practice to be discovered by many of today’s savvy medical cannabis cultivators.

The Future Is Here: Growroom and Reservoir Control

Automation technhydrology is growing by leaps and bounds—just check out the home automation section at your local building center for proof. For cannabis growers, switches that can turn things on and off independently when you need them to are invaluable tools. A light timer is a perfect example.

Let sensors do the work for you.

We’ve arrived at the dawn of AI (artificial intelligence) in the growroom. One such example is Grohaus Automation’s hydroponic reservoir control. Sure, the device can inject pH Up or Down and any ratio of nutrients and supplements via touch-screen programming—that’s all good, and save for the touch screen, these are already well-established technologies for sophisticated hydro growers.

Where the real quantum leap comes in has to do with the fact that the control thinks before acting. Seriously—the program watches your reservoir and the conditions (it can be set for higher or lower flow rates and aeration levels) and, once it learns the rhythms of change, will execute real-time adjustments after making intelligent assessments. For example, instead of adding pH Down the second the res value changes, it might wait an hour—because it knows it will need to add more fertilizer soon, and the reaction when concentrate is introduced to the reservoir by the micro-dosers will lower the pH on its own. Smart growers know that continuous additions of pH buffers can shift the reservoir’s chemistry over time, possibly causing uptake issues for hungry cannabis plants.

Reservoirs are the engine of hydroponic growing.

There are other game-changing advances in controls and concepts that have begun to surface for hydroponic growers, including cloud-based technologies offering total growroom control. It’s getting easier (and more efficient) to be productive, which means either less time fussing in the garden or the ability to grow more (or bigger) with no additional labor. And this means, in turn, that the future is looking bright for cannabis and the dedicated people who grow it.

The 5 Habits of Highly Effective Hydro Growers

By Erik Biksa

Cleanliness is important to hydro success.

1. Work smarter, not harder:

Hydro allows growers not only to enjoy faster growth rates when it’s done right, but also to spend less time doing it. A stable hydroponic solution and a fresh reservoir top-up via a float valve is something anyone can master. This allows a single grower to yield much larger crops—because he (or she) can afford the time in other areas required for successful growing, such as pruning and harvesting.

2. Stay consistent:

Cannabis plants have an amazing ability to adapt to a variety of situations, but they often produce best when given a consistent and stable environment. It’s okay, for example, to have differences in temperature between day and night—but a stable pH and a steady EC (or ppm level) in nutrient formulations made specifically for hydroponics and applied at the same daily intervals, or continuously, will result in superior plants.

3. Be slow to change:

Hydroponic systems can be incredibly responsive—much like a performance racecar’s acceleration—when growers make changes to the feeding program. You can see changes in hours instead of days when it comes to hydro, because nothing gets in the way of the roots absorbing supercharged nutrient solutions. However, this also means that you shouldn’t make drastic changes, but rather gradual ones, so as not to lose control and crash and burn (or not burn, as the case may be, because your buds got overfertilized and won’t smoke right).

4. Stay chill:

Take advantage of the natural laws of thermodynamics. In simple terms, you can run a slightly warmer growroom, which can result in big power savings from reduced cooling when you use water-culture methods, and cool the nutrient solution rather than the air. Essentially, the plants’ response to temperature has more to do with their internal temps and less to do with the temperature of the air. So a plant filled with water that was supplied at 68°F at the roots will stay cooler even when surrounded by warmer air. And when you add CO2 to a warmer environment, it’s like nitrous at a drag race—stand back and watch them go super-fast!

5. Keep it clean:

For professional medical producers and home growers alike, the “clean” factor of hydroponics is a big advantage. If you use natural principles and inert materials to cultivate plants, as in pure water-culture methods, your finished buds are far more likely to be free of any potential contaminants. And the same is true for the surrounding area, since hydro growing means fewer occurrences of problems like insects or diseases that may surface in “dirty” growing environments.

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