Beginner’s Guide to Growing Marijuana with Hydroponics

Successful marijuana growers will often claim that hydroponics is a challenging and complicated process, mainly to discourage their competition and continue their dominance in the cannabis market. While hydroponics systems may present some unique challenges that don’t pertain to growing in soil, it has advantages and benefits that far surpass traditional growing methods. Hydroponics is also low maintenance and very simplistic once your indoor marijuana garden is setup properly. If you’re just getting started with hydroponics, this beginner’s guide includes numerous growing tips that can be extremely helpful to you. Remember, a big part of becoming an experienced hydroponics grower is about understanding plants and proper gardening techniques.

Photosynthesis allows plants to produce carbohydrates, a fuel source that essentially acts as food for the organism. Photosynthesis relies on carbon dioxide (CO2), light (grow lights) and hydrogen (water). Oxygen is a by-product of this process, which is why you commonly hear that plants provide the earth’s oxygen. Light, carbon dioxide and water are the key variables to photosynthesis.

Understanding Nutrient Solution

Nutrient enriched water is how hydroponics systems function. Maintaining the correct strength in this nutrient solution is very important and thanks to today’s electronic devices, it’s very easy to do. However, it’s still important to understand exactly how these devices work. Pure water does not conduct electricity. If you allow salts to dissolve into the water, it will. The electrical current in the water will flow stronger as more salt is dissolved into the solution and the electrical current can be monitored to determine the overall strength of the nutrient water.

These devices use a scale consisting of electrical conductivity (EC) or conductivity factor (CF). In hydroponics, the most commonly used scale is CF. The CF scale ranges from 0 to 100 and the optimal range for your nutrient water is dependent on the type of plants that you are growing.


Germination is a term used for when a seed starts to grow. Seeds are placed into a growing medium such as perlite to be germinated. For this to work properly the seed must be alive and active. Seeds can be in dormancy, which will prevent germination. Most plant seeds will need to be kept within a very specific temperature range. Oxygen and moisture must also be available to the seed. For some seeds there may even be lighting conditions that must be met.

When the plant first appears you will generally see two leaves. These are called cotyledons or seed leaves. These are not the plant’s actual leaves. Instead, they are there to serve as a food source, allowing the plant to consume itself for growth.

Grow Medium

Soil is not present in hydroponics systems. Instead, a grow medium is used and the roots are supported by this medium. Some mediums will even aid the the grow process by providing moisture and proper nutrient retention to the plant. This is why there are different varieties of grow mediums, as each medium has its own advantages and can be used for specific plants. It’s a good idea to do thorough research on the plant you are growing and its recommended grow medium. Popular grow mediums include:

Perlite, composted bark, expanded clay, oasis, gravel, peat moss, rockwool, sand, pumice and vermiculite.

New grow mediums are often experimented with by hydroponic growers in order to get the best harvests. There are many grow mediums that have successfully been used before that are not listed here.

The Hydroponic System

There are two basic types of hydroponic systems: water culture and media-based. Water culture does not use a growing media, while media-based does. Media-based is the most common of the two for indoor hydroponics. Both systems can be either passive or active. An active hydroponics system will have pumps and timers that run the system. This is common in a hydroponics system that is drip fed, where the water is fed to the plants from above, using a tube. A passive system may have its fair share of gadgets, but it will not use pumps to supply the nutrient water to the plants. Passive systems usually have a reservoir of water that resides below, allowing the plant’s roots to grow within the water.

Grow Lighting

Plants need a light source to undergo photosynthesis and thrive. Proper lighting is very important to plant growth and it’s an essential component to any hydroponics system.

Natural Light vs. Artificial Light

Not all light is created equal and because the sun radiates the full spectrum of light, it’s often preferred among gardeners. Full spectrum lighting means the complete wavelength / color of light. Although artificial light can replicate this, it’s generally not as efficient as the sun. With that being said, the majority of hydroponic growers are using indoor gardens where sunlight is simply not accessible. If there’s a window seal or some other spot where light can be accessed, this is usually the best location for growing.

Light is the most important factor in plant growth. By reducing the plant’s access to light by 20 percent, you will usually reduce the performance of the crop by 20 percent as well.

Most hydroponics growers are using a combination of LED grow lights and grow light ballasts/reflectors. This provides the maximum amount of light for an indoor garden.

The Macronutrients

There are about 16 mineral nutrients that are important to plant growth. Nitrogen (N), phosphorus (P) and potassium (K) are used by a large variety of plants and in large amounts. You will often find these nutrients on fertilizers and other plant nutrients displayed as hyphenated numbers such as “15-15-15.”  These numbers correspond to the percentage by weight of these macronutrients. Sulfur (S), magnesium(Mg) and calcium (Ca) are considered macronutrients as well.

Each nutrient plays a different role in plant growth.

  • Sulfur – provides healthy leaves with dark green colors
  • Calcium – Benefits root and plant growth
  • Potassium – Provides resistance to diseases and aids the plant in extreme temperatures
  • Magnesium – Chlorophyll – Provides green color and helps the plant absorb sunlight and undergo photosynthesis
  • Nitrogen – Allows the plant to develop new leaves
  • Phosphorus – Provides aid with root growth and aids the blooming cycle

The Micronutrients

There are many other nutrients that are generally only found in small quantities in plants. These include cobalt (Co), boron (B), copper (Cu), iron (Fe), zinc (Zn), manganese (Mn), and molybdenum (Mo). These are considered micronutrients. Plants generally get these nutrients from the soil and therefore, a lot of fertilizers that you find in stores do not contain them. For hydroponics systems, it’s important that the nutrient solution contain micronutrients due to the absence of soil.

Nutrient Solution

With hydroponics, a nutrient solution is added to the water to provide food for the plants. In traditional gardening, plants get the nutrients they need from the soil. In hydroponics, the plants rely on the nutrients within the water. There are many different types of nutrient solutions on the market. Often times, there will be different nutrients for the various growth cycles. There are also nutrient solutions designed for specific plants.

Osmosis and its involvement in hydroponics

A plant’s roots are not open-ended, which means water and nutrients do not flow through the root like you may think. A plant’s roots do not simply “suck up” water from the nutrient solution. Instead, water and nutrients are able to enter the root from the bottom, sides, and top due to osmosis, a natural energy that allows elemental ions to move through what you might observe as solid material. This is much like putting water on ordinary paper. Although paper appears to be solid, you’ll notice the opposite side of the paper becoming wet as the natural energy force moves the water through to the other side.

If you use a nutrient solution that is too strong, reverse osmosis can occur and the plants will die. Rather than the nutrient solution making its way into the root, the nutrients from the root will be expelled back into the water. Now that you know how osmosis works and its importance in nutrient solution and water retention in roots, you can use this information to your advantage to supply a high nutrient solution to your plants, without over fertilizing.


Plants expel oxygen as a result of photosynthesis. At night when light is no longer available to the plants, the process reverses. The plants will use the energy from the oxygen that was stored throughout the day.

Air Pumps

In order to keep the nutrient water active and provide oxygen to the roots of the plants, an air pump is used. The air pump is typically placed outside a water culture hydroponics system and by using tubing or an air line, it connects to an “air stone” that resides at the bottom of the water reservoir. Once turned on, it pumps air through the tube, into the air stone, where bubbles of oxygen are created that float to the top of the water.

Pests and Disease

Pests and diseases are one of the biggest concerns when growing in soil. By using hydroponics, you dodge this issue almost entirely, but it can still cause major concerns. Fusarium, verticillium, cladosporium and botrytis are the most common types of bacteria that affect hydroponic growers. Insects that commonly cause issues include fungus gnats, nematodes, thrips, spider mites, caterpillars, cutworms, aphids, lead miners and whiteflies.

Hydroponic growers can prevent an infestation or infection from diseases by:

  • Make sure the grow environment is highly sanitary
  • Grow plants that are resistant to pests and diseases
  • Maintain proper ventilation and monitor the temperature of your plants and nutrient solution
  • Commonly check the plants to stop the problem early should it arise

Once a plant becomes overwhelmed by pests or disease, it should be discarded immediately. The entire crop could potentially be lost. With insects it’s easy to remove and kill them but there are also sprays and solutions for smaller critters.


The pH value of your nutrient solution measures the concentration of positive hydrogen ions. The way your hydroponics system filters and mixes air into the nutrient solution will determine the number of negative hydroxyl ions that are produced. Plants exchange ions in order to feed. When large numbers of ions are consumed by the plants, their growth is faster, but the pH value in the nutrient solution will rise. If the solution has a pH value of 7.0, then the amount of hydrogen ions is relatively equal to hydroxyl ions. If the pH is below 7.0, then the hydrogen ions have outnumbers the hydroxyl ions. If above 7.0, there are more hydroxyl ions and this is known as a “alkaline” solution.

pH testing kits are essential to hydroponics systems. Regularly monitoring the pH value of your nutrient solution is very important. The value that you want in your nutrient solution is dependent on the types of plants that you are growing. It’s always a good idea to test the pH value before adding nutrient solution to the water.

Mineral / Nutrient Deficiency Symptoms

If you haven’t added your nutrients correctly and there is a mineral deficiency in the water, there will be some noticeable symptoms.

When nitrogen becomes deficient the leaves of your plants will typically start to turn yellow. This will be especially true in older leaves. New roots will have stunted growth.

When phosphorous becomes deficient there may be a dark green color in the leaves and the plants will also experience stunted growth. The stems of the plants may appear to turn purple.

Iron deficiencies result in the leaf veins turning yellow. The yellowing will typically appear in the youngest leaves. Leaves can turn white if the iron deficiency continues.