Hydroponic Garden Ventilation

greenhouse ventilation

Why is hydroponic ventilation necessary?

To maintain adequate hydroponic grow room ventilation, grow room fans can be used to control humidity, temperature, and carbon dioxide levels. A grow room fan or hydro fan within a grow room is essential for a number of reasons.

By exchanging, circulating and mixing the air, a hydroponic ventilation will give you more control over the following growing conditions.


Inadequate ventilation can lead to high humidity and this can result in a number of problems for the plant at various stages of growth. A humidity of 60% RH (Relative humidity) is recommended during vegetative growth and around 40% RH during flowering to prevent flowers or fruits from rotting.

HYdroponic ventilation will also help to prevent fungal diseases as fungal spores thrive in humid, stagnant air. Stale stagnant air also provides other airborne pests such as sciarid flies a greater opportunity to infest your grow room.

Hot air holds more water vapor so by extracting hot and humid air and replacing it with cooler less humid air, high humidity will become less of an issue.

Carbon Dioxide

Plants need carbon dioxide (CO2) to grow and photosynthesize and this is essential for plant growth. Plants within any confined space will soon use up that carbon dioxide.

Therefore, a hydroponic extraction fan is necessary to maintain high levels of carbon dioxide and ensure a fresh supply of air into the grow room. We recommended that you try to replace the air in your grow room at least 20 times per hour or every 3 minutes to maintain a reasonable air quality.


Hydroponic lights within a grow room can produce a lot of heat. When the lights are on the temperature should range between 21 to 28 degrees centigrade (70 to 82 Fahrenheit). Try and reduce this temperature by about 5 degrees Celsius (9 degrees Fahrenheit) at night as this is important for correct flower maturation.

Grow room ventilation using a hydro fan will help maintain the correct temperature. A hydroponic fan speed controller will enable greater control of the temperature as they can be controlled by a thermostat.

A fan speed controller linked to a thermostat will enable you to vary the speed of the hydroponic fan automatically depending on your preferred air temperature.

Hydroponic Fans

Good hydroponic ventilation is essential for healthy plant growth. It is one of the most important factors to consider when growing plants within an enclosed space. Ventilating a grow room or grow tent involves selecting the correct size exhaust fan or extractor fan and maintaining a fresh supply of air from outside.

We created this section of our guide to help you choose the correct hydroponic fan for your grow room. We also provide guidances on the best setup and recommended method for installing a hydroponic fan.

What Size Fan Should I Buy?

Buying an adequate sized fan for your grow area is important as the cost of a hydroponic fan will largely depend on its size and power. Generally speaking the longer the length of the fan the greater the volume of air that can be extracted at any given minute.

However, fan designs can vary significantly and you will want to know the Cubic Feet per Minute (CFM) value of the fan. CFM specifies the volume of air in cubic feet extracted every minute.

Firstly calculate the area of your grow room or grow tent. Multiply the room’s length by the width by the height. So for example for a 7 foot by 6 foot by 10-foot area, the volume would be 7 x 6 x 10 = 420.

The extraction fan/exhaust fan should exchange the air in the room at least once every three minutes. So simply divide the area in cubic feet by three minutes to calculate the minimum CFM: 420 / 3 = 140 CFM

If you plan to use a carbon air filter (more on that later) multiply by 30%: 140 x 1.3 = 182 CFM.

This is minimum recommended air flow rate and once this has been established you should buy a hydroponic fan with a similar air flow rate.

Vent Hole Size

The grow room must include a vent hole to draw air into the room while the hydroponic extractor fan is drawing air out. The vent hole needs to be at least the same size as the size of the extractor. For example, if you are using a 7-inch extractor, the size of the inlet hole should be at least 7 inches but preferably slightly larger to reduce drag.

Also, air drawn in through the inlet hole needs to be near to the ground were as the extractor fan drawing air out needs to be positioned near the top of the grow room or tent. This will enable better air circulation and mixing and also remove the hot air that tends to rise.

Intake and Extractor Fans

An intake fan can be used in conjunction with an extraction fan to pull air out of the grow area. An intake fan is the same as an extraction fan. However, it is used to pull air into a grow room instead of removing air. The extractor fan should be positioned at the top and preferably on the opposite side of the intake fan.

Whether you use an inlet hole or an intake fan, the important thing to remember is that the fan pulls fresh air from outside.

If you chose to use both intake and extractor fans, the combined CFM of both fans must total to the required CFM. Therefore, if you require 182 CFM, one fan could be 140 and the other 42. However, the intake fan should always have a lower CFM. It should preferably be a third to a half of the extractor fan.

Having two fans working together provides better control of humidity and temperature; it creates negative air pressure within the room and prevents smells from escaping back through the ventilation system. You will also discover that the fans will be less noisy and last longer.

Sometimes you have to move air to an exterior vent or move air a distance from an outside wall. If so, you may need to use ducting. Ducting comes in standard sizes that should fit all of your fans and filters. Flexible ducting is easier to work with, but it is important to try and keep it straight.

Your ducting should be as short and straight as possible. You should try and avoid bends in the ducting. These bends will create drag that in turn creates noise as the air moves through. It will also lower the efficiency of the grow room fans and may require more powerful fans to compensate.

Buying a Carbon Filter

If the exhaust from your grow room smells you can do something about it. You can use a hydroponic carbon filter with your grow room extractor fan. Carbon filters, also known as carbon scrubbers, will remove almost all of the odor from the air before extraction. You should replace or refill carbon filters periodically.

Normally you would have a setup like the following. You place the fan and filter inside the grow room or grow ten. The fan draws the air through the filter before leaving through some ducting to the outside.

If the growing area is too small you can get away with placing the hydroponic ventilation fan and filter outside. This frees up space inside the grow room.

This way, the extraction fan pulls stale air out of the grow room through some ducting. Since the fan is located outside, the air if pulled through it and through more ducting. The fan also pulls the air through the filter during extraction.

Other Accessories

Fan speed controller: A fan speed controller controls the speed of the fan. If the fan speed controller uses a thermostat to regulate the temperature of the grow area. This is more efficient, reduces noise and prevents the temperature and humidity from being too high or low.

Acoustic ducting: If the fans are too loud you can use acoustic ducting to reduce the air turbulence noise. Fix a silencer on each end of your fan to get the full benefits.

Hydroponic Guide Sections

To learn more about other aspects of hydroponic gardening, see the following sections of our guide.

Hydroponic Air Pumps

What are Hydroponic Air Pumps?

You use a hydroponic air pump to pump air into a hydroponic nutrient reservoir. Air stones inside your hydro tub convert the air into small bubbles. You connect these air stones to your air pump with an air-line tube. The bubbles produce oxygen inside your nutrient reservoir. The roots absorb and utilize the oxygen in the nutrient solution.

Plant root systems require water, nutrients, and oxygen. Aerating the roots improves nutrient update and water absorption increases cell growth and activity. Scientists have proven that increased oxygen to the root system can increase crop yields. Aerating the water also prevents the nutrient solution from becoming stagnant which can lead to root rot and other problems.

Hydroponic air pumps are a cheap and effective way to provide oxygen to your plants. All you need is an air pump, air stones, and an air-line to connect the air stones to the air pump.

Buying a Hydroponic Air Pump

A regular air pump designed for an aquarium is all you need for most setups. You can choose from many brands.

Some manufacturers design air pumps for hydroponics although other pumps are specifically for aquariums. However, they all do much the same thing. The pumps produce air that the air stone converts into bubbles. In turn, the bubbles oxygenate the water in an aquarium or hydroponic reservoir.

When buying a hydroponic air pump there are a number of factors to consider and specifications listed by the manufacturer. The following sections describe those considerations.

Open Flow

Open flow or maximum capacity is the maximum flow of air produced without any restriction on the air being drawn by the pump. Specifications typically describe the Open flow in liters or gallons per minute or hour.

The amount of air that can be pumped into a hydroponic reservoir is affected by airflow resistance or drag. You determine the airflow or drag by the length of the tubing and the depth and pressure of the solution. The greater the PSI of an air pump, the more freely the air will flow.

PSI (Pounds per Square Inch)

Air pump specifications often specify the PSI. The higher the pressure the lower the drag. A higher PSI means the air will flow more freely through the tubing into the reservoir.

Noise Level

Noise Level measured in Decibel (dB). Some less efficient air pumps are noisy. This can be a nuisance with indoor hydroponic growing systems. People say that air pumps produced by Secoh, a Japanese company, are almost silent in operation as well as reliable, efficient and high quality.

Maximum Power

In most cases, we would measure maximum electrical power consumption in watts. The higher the power, the greater the airflow. While some brands and devices are more efficient than others, a general rule-of-thumb is 1 watt for every gallon of nutrient solution.

Life Expectancy

Usually measured in hours, this is the estimated time that the device will maintain the specifications given. You can improve life expectancy by replacing parts that get worn or damaged.

Number of Outlets/valves

The number of outlets on an air pump will determine how many air stones and air-line tubings you can connect to the air pump. This is useful if you have your plants situated in a number of different buckets or barrels and need an air stone in each container. Some air pumps can have as many as 12 outlets.

Tubing Size

Air pump tubing size is the inner diameter of the tubing. This tubing is connected to the air pump valves. The specifications usually specify either inches or centimeters.


The price of an air pump will depend on the brand, wattage, materials, and accessories that come with the air pump. You don’t have to spend much on a hydroponic air pump. You can buy a cheap air pump for around $20 – $45 that would be suitable for most indoor hydroponic systems.

Another factor to consider is whether the air pump is rainproof. If you’re intending to use the air pump outside, a rainproof enclosure will protect the air pump from rain or splashes of water.

What is the Best Air Pump Brand?

The following air pump manufacturers produce air pumps that can be used for both aquariums or hydroponic systems: Rena, Hiblow, Secoh, Alita, Koi, Medo, EcoPlus, Hakko, General Hydroponics, and Danner.

  • General hydroponics – they produce the dual-diaphragm air pumps boast that they are the only brand that specifically builds air pumps for hydroponic systems. However, you can use any aquarium pump in a hydroponic system.
  • Secoh Septic – many gardeners say that this pump is almost silent in operation as well as one of the most energy-efficient hydroponic pumps, it is both reliable, and of high quality. They claim to have won the best pump in just about every independent review. However, because it is a foreign company finding spare parts that need replacing may be more difficult. They can also be pricey.
  • Eco Air – People consider this pump to be quiet, efficient and long-lasting with a controllable variable output on some models. They also operate without the need for oil.

Air Pump Accessories

Air Stones

Stones come in different shapes and sizes with the most common being golf ball or cylindrical-shaped. Air stones convert air from the hydroponic pump into a gentle flow of bubbles that rise to the surface. Oxygen is essential to plant. The nutrient solution absorbs the oxygen in these bubbles so the plant roots can use it effectively.

Micro-pore diffusers

Micro-pore diffusers are similar but superior to air stones because they produce a larger quantity of smaller more prolific bubbles over a larger area. They tend to be more long-lasting than air stones and do not clog up so easily. Manufacturers create diffusers with kiln-fired ceramic material that does not react with nutrient solutions. You can buy single or double micro-pore diffusers.

Air Dividers

You can connect air dividers or port manifolds to an air pump to create multiple outlets for several air stones or diffusers. This provides a much greater spread of oxygen.

Air-line Tees

Similar to air dividers or port manifolds, gardeners use airline tees for adding an additional line to an existing air-line or making two outlets from one pump outlet.

Air-line Tubing

Often made of clear silicon air-line tubing fits your pump or manifold and allows air to flow through easily to the air stone or micro-pore diffuser. You should use the same length of line to each stone for equal delivery of air into the water.

Air Pump Maintenance

Air pumps require regular maintenance every few months. This can involve replacing diaphragms and filters to keep them running. You should buy an air pump from a manufacturer that you can easily obtain spare parts from. The Tetra Whisper AP300 is one of the best hydroponic air pumps on the market and a replacement kit should only cost a few dollars and are readily available.

Make sure you have a non-return valve in the air-line to stop the water siphoning back up the air pump and destroying it. This can happen when the pump is positioned below the reservoir.

Valve Blocks

You should replace valve blocks when the pressure fails or when the pump is functioning less efficiently. These valves do wear out over time and this can result in air leads and lower efficiency. You can lengthen the life of these valves by changing your pump’s air filter monthly.


These filters are usually round and mounted to the bottom of some air pump models. They should be replaced when dirty to avoid damage to the air pump valves and to reduce the chances of the diffusers becoming clogged up.

Air stones

Over time there will be a buildup of salts from your nutrients, these can clog up your air stones. However, you should be able to remove the clocked materials using a soft toothbrush.

Hydroponic Guide Sections

To learn more about other aspects of hydroponic gardening, see the following sections of our guide.

Hydroponic Grow Lights

The best hydroponic grow lights for you will depend on a number of factors. These include:

  • Cost of the light (energy cost time X number of hours)
  • The plant environment
  • The stage of growth

Fluorescent and Incandescent grow lights

While they are cheap to buy incandescent bulbs are rather inefficient as hydroponic grow lights.

Incandescent and fluorescent grow lights are fine for low-light plants when you expect limited results. However, the light is low intensity and they produce a low level of lumens per watt and are therefore less efficient than High-Intensity Discharge lights (HID) or Light Emitting Diode (LED) grow lights.

Incandescent lights have a much shorter usable bulb life than high-pressure sodium lights and LED grow lights. They also have approximately six times lower light output per watt of energy consumed than a High-Pressure Sodium (HPS) light.

High-Intensity Discharge Lighting (HID)

High-Intensity Discharge lighting consists of a lamp, reflector and power supply. Manufacturers design these lights to produce a high output of photosynthetically active radiation (PAR) for the amount of power consumed. It is not just the quality of the light but the quantity that is also important and High-intensity discharge lights can produce both.

Commercial growers and some of the world’s premier growers use High-Intensity Discharge lights and produce impressive results that would be impossible with conventional fluorescent and incandescent lamps.

Until recently High-Intensity Discharge lighting for horticulture has not been cost-effective. As a result of new lighting products by manufacturers like Hydrofarm and Sunlight Supply, lighting costs have been significantly reduced making the use of such lights profitable.

High-Intensity Discharge lights cover the PAR spectrum (Photosynthetically Active Radiation). The wavelengths of light most important for photosynthesis to occur are the red and blue light spectrum, red being 600 – 680 nm and blue is 380-380 nm. Scientists consider these wavelengths the most important for photosynthesis and HID lights cover these spectrums well.

There are two types of HID lamps which emit different color spectrums.

Metal Halide (MH) Grow Lamps

Metal halide lamps emit light at the white/blue spectrum. Metal Halide lamps are best used as a primary light source if there are no other light sources and little or no natural sunlight is available. They consume large amounts of energy but produce significant quantities of light.

Advantages of Metal Halide Lamps:

  • Best when there are no other light sources
  • Promotes compact vegetative growth
  • Best for vegetative growth
  • Emit high levels of blue light promoting growth of leafy plants

High-Pressure Sodium (HPS) Grow Lamps

High-pressure sodium grow lights have a long usable bulb life and are a much more efficient means of producing light than standard incandescent grow lights. They emit a yellow/orange spectrum of light and have a yellowish glow. They are good when you use them in combination with other light sources such as weak sunlight during the winter months.

Advantages of High-Pressure Sodium Lamps:

  • Work well with other light sources (natural sunlight etc)
  • Best for flowering/budding stages of growth
  • Ideal for a hydroponic greenhouse or commercial growing application
  • Emit high levels of red light good for flowering and fruiting plants

The Hortilux HPS lamps add an additional 30% blue factor to their spectrum making them more efficient than other HPS lamps for solo use.

You can also buy High-Pressure Sodium to Metal Halide conversion bulbs. These can switch from emitting Metal Halide light during vegetative growth then let you switch back to High-Pressure Sodium for the flowering/budding stage of growth.

LED Lights for Hydroponic Gardens

What are LED Lights?

LED grow lights are the most efficient means of producing light for plant growth. The light produced targets narrow wavelengths required for photosynthesis. Furthermore, most of the energy is not lost in the form of heat like with other grow lights. LED grow lights have the highest PAR value (photosynthetically active radiation) of all grow lights.

The downside of LED grow lights is that they are expensive to buy and while being the most efficient, the cheaper models don’t produce enough lumens to be effective for growing a decent size crop.

LED lights are just small light bulbs that can fit easily into an electrical circuit but unlike ordinary incandescent bulbs, they don’t have a filament that burns out, and they don’t get very hot. Therefore, they last a lot longer. You can also configure lights to emit light at a specific wavelength. This makes them more efficient for growing plants which require light between 400 to 700 nanometers.

Advantages of LED Grow Lights:

  • Produce less heat than other light sources which can damage plant and dry up the hydroponic solution
  • Much longer bulb life than other lamps. Typical lifetimes quoted are 25,000  to  100,000 hours
  • Lower energy costs due to higher efficiency
  • No costly cooling system required unlike Halide Lights which get hot
  • LED grow lights do not contain the harmful mercury-filled bulbs that exist in some other grow lights
  • Powerful LED grow lights have been shown to produce higher yields and vegetative growth

Efficient Means of Producing Light

Thanks to new technology LED grow lights have become the most efficient means of producing artificial light for plant growth. This is because LED grow lights have a high photosynthetic photon flux (area) density for every Watt consumed. What does this mean?

Photosynthetically Active Radiation

hydroponic grow light -- plant light spectrum

According to Wikipedia “Photosynthetically active radiation, often abbreviated PAR, designates the spectral range (wave band) of solar radiation from 400 to 700 nanometers(nm) that photosynthetic organisms are able to use in the process of photosynthesis”.

Photosynthetic Photon Flux Density (PPFD) refers to the photosynthetically active radiation emitted per square meter per second. In other words, it is the energy suitable for plant growth emitted every second for every square meter of the plant.

The higher the PPFD the higher the crop yield as the light can cover a larger area.

Plants only require light energy within a narrow frequency of between 400 and 700 nanometers (nm’s) and other frequencies can even be harmful to a plant. A frequency too high can damage the cells and a frequency too low won’t penetrate the plant.

Because hydroponic LED grow lights can be manufactured to emit light at narrow wavelengths specifically suited to plant growth they are more efficient and don’t require as many watts to run as other grow lights.

How to Measure Hydroponic Grow Light Efficiency

The efficiency of a LED grow-light is determined by PPFD per watt of energy. The PPFD per watt will determine how efficient a light source is at producing photosynthetic active radiation per watt of power.

The efficiency of an LED grow light can be expressed as the number of grams of crop produced per watt. However, this will vary depending on the plant and other environmental factors.

Since the photosynthetically active radiation range occurs within the visible spectrum it is common for the brightness of the light to be measured in lumens or lux.

If these lights are left on 24 hours a day and use a high wattage they can still run up your energy costs. You want a powerful LED grow-light that produces a high plant yield but efficient enough that it consumes relatively low wattage.

Hydroponic Guide Sections

To learn more about other aspects of hydroponic gardening, see the following sections of our guide.

Hydroponic Nutrient Solutions

hydroponic nutrients

Introduction to Hydroponic Nutrient Solutions

Are you are an experienced hydroponic gardener? If not, we recommend that you buy pre-mixed hydroponic nutrient solutions. It can be difficult for a beginner to make a homemade hydroponic nutrient solution yourself.

Many gardeners don’t want to go to the bother of making their own hydroponic nutrients. Ready-made hydroponic nutrients usually provide a balanced diet. This will allow you to focus on other aspects of plant care.

You can adjust your nutrient solution later depending on the stage of development and conditions of the plants. However, ready-made hydroponic nutrients are more manageable. In addition, their nutrient concentrations are easily identifiable.

You can find hydroponic nutrients for sale at many large nurseries and hydroponics stores. These usually contain all the essential nutrients and trace elements.

The best hydroponic nutrient brands provide nutrient solutions containing essential macro and microelements. They also include crop enhancers because they give your plants an extra boost. For example, they typically include root boosters, amino acids, microbes, enzymes, vitamins, F-1 (fulvates), H-2 (humates) and a non-ionic surfactant.

Choosing a Nutrient Brand

Choosing between brands can be confusing and it can be expensive and time-consuming to do comparison testing. Based on our experience, these exotic nutrient solutions can make a big difference to yields.

There may not be much difference between manufacturers. However, you should avoid lesser-known hydroponic nutrient suppliers. Many of these “hydroponic nutrient manufacturers” don’t actually make all of their own products. Sometimes the manufacturers sell a very different product to you because they switched suppliers. This can harm your plants.

The best hydroponic nutrients will depend on many factors. There are many variables that need to be controlled to carry out a successful comparison.

To discover the best hydroponic nutrients for your plants you should do your own experiments. We recommend setting aside a few of your plants for that purpose. Be sure that you place them in the same environment to ensure accurate test results.

Commercial Nutrient Solution Providers

General Hydroponics – Hydroponic cultivation by NASA on the International Space Station is done with help from General Hydroponics. They claim to be at the cutting edge of scientific research into hydroponic systems and perfecting nutrient formulas.

Advanced Nutrients – Advanced Nutrients provide 2-in-1 and even 5-in-1 solutions that contain base nutrients with added ratios of chelated macro and microelements. They have a large selection of solutions and formulas to suit your skill level and needs. In addition, Advanced Nutrients claims to have developed the first-ever pH-perfect nutrients.

Botanicare – Botanicare first started developing experimental plant nutrients in 1999. Since then, they have grown into a leading nutrient provider. They provide an online nutrient calculator that could be useful for your hydroponics activities.

CANNA – A Dutch company, CANNA products with a wide range of high-quality gardening fertilizers and plant nutrients.

Fox Farm – This company is a family business dedicated to producing the finest quality garden products available anywhere. Their soil mixes, soil conditioners, and fertilizers are specially formulated to replenish the soil.

Technaflora – This is a Canadian company offering a variety of nutrients and additives for hydroponics and specialty gardening.

Dutch Masters – This is a family-owned brand of plant fertilizers, originally from Australia. However, they are now global. They specialize in optimal nutrition for cannabis plants.

DIY Hydroponic Nutrient Solutions

hydroponics salt

If you believe you’re experienced enough to create your own hydroponic homemade nutrients, we recommend you use fertilizer salts.

These are the most common type of homemade hydroponic nutrients and are very basic and cheap, assuming you can buy them in small quantities.

You can buy them in bulk from plant food suppliers, plant nurseries, and agricultural agencies. Unfortunately, if you buy hydroponic fertilizer salts from these suppliers you often have to buy in twenty-five to fifty-pound bags.

This will not be practical or cost effective for you unless you are buying for a large-scale commercial business or an extensive hydroponic garden. We recommend that you instead buy fertilizer salts from online sites such as Amazon because these suppliers sell them in smaller quantities.

Here’s a list of recommended fertilizer salts for those who want to make their own hydroponic homemade nutrient solution.

SaltWhat it supplies…
Magnesium sulfate (Epsom salts)Magnesium and Sulphur
Potassium sulfatePotassium and Sulphur
Potassium nitrateNitrogen and Potassium
SuperphosphatePhosphorus and Calcium
Calcium sulfateCalcium and Sulphur
Ammonium phosphateNitrogen and Phosphorus

The following is a workable, tried and tested hydroponic homemade nutrient solution. However, there are many different nutrient formulas. If you include the elements in balanced amounts, the plant should be fine. The plant will extract from the solution what it requires.

Above all, every plant is different and exists in different conditions. You should experiment with what works best for you.

The recommended quantity is the weight in ounces that experts recommend in a 100 Imperial (120 American) gallon water solution.

Homemade Hydroponic Nutrient Solution

Ammonium sulphate1.5 ounces
Potassium nitrate9 ounces
Monocalcium phosphate4 ounces
Magnesium sulfate6 ounces
Calcium sulfate7 ounces

Combine the element with trace elements and 100 gallons (120 American gallons) of water, or 1 ounce per 3.7 Imperial gallons.

In addition to the three key elements of nitrogen, phosphorus, and potassium you should include at least 8 trace elements in your nutrient solution. These include zinc, copper, sulfur, manganese, iron, calcium, magnesium and boron, chlorine and molybdenum.

Chlorine and molybdenum are already present in either the water supply or salts mentioned above. You should add those because this will avoid toxicity.

Function of each element in a hydroponic solution:

Trace ElementFunction
NitrogenNecessary for the production of leaves and in stem growth. An essential ingredient in building plant cells.
PhosphorusRequired in the development of flowers and fruits and aids in the growth of healthy roots.
PotassiumUsed by plant cells during the assimilation of the energy produced by photosynthesis.
SulfurAssists in the production of plant energy and heightens the effectiveness of phosphorus.
IronVital in the production of chlorophyll. Manganese aids in the absorption of nitrogen. An essential component of the energy transference process.
ZincAn essential component in the energy transference process. Copper needed in the production of chlorophyll.
BoronRequired in minute amounts, but it is not yet known how the plant uses it.
MagnesiumOne of the components of chlorophyll, magnesium also is involved in the process of distributing phosphorus throughout the plant.
CalciumEncourages root growth and helps the plant absorb potassium.ChlorineRequired for photosynthesis
MolybdenumAssists in some chemical reactions.

The trace elements that are added to these formulas must be mixed separately. One recipe is given below. Note that you can use a mortar and pestle to grind elements to a very fine powder.

Trace elements Solution

Zinc sulfate½ teaspoon
Copper sulfate½ teaspoon
Iron sulfate1 ounce
Manganese sulfate1 teaspoon
Boric acid powder1 teaspoon

These ingredients should be ground well and stored dry and you should use half a teaspoon per 100 gallons or 120 American gallons of water.

Hydroponic Guide Sections

To learn more about other aspects of hydroponic gardening, see the following sections of our guide.

Hydroponic Growing Medium

hydroponic grow medium

What is a good hydroponic growing medium?

A good hydroponic growing medium has the following properties:

  • Should be able to stay pH-neutral and buffer pH changes
  • Hold nearly equal concentrations of air and water
  • Able to hydrate and re-hydrate quickly
  • Can be recycled/reused and is biodegradable
  • Cheap and easy to obtain
  • Lightweight and easy to move around both outdoors and indoors

The best hydroponic medium also depends on the type of hydroponic system you will use. Hydroponics gardeners most commonly use coconut coir, agricultural grade perlite, expanded clay pellets, Rockwool and common pea gravel as a growing medium.

Other less common growing mediums include composted bark, gravel, oasis, peat moss, pumice, sand, sawdust, soilless mix(s), vermiculite and gravel.

You can mix mediums together. For example, gardeners often use coco coir mixed with 50/50 perlite to provide a higher air holding ratio than coconut coir alone.

Popular Growing Mediums

Coconut Coir

Coconut Coir

Many gardeners like coconut coir, otherwise known as coconut fiber, as a growing medium. Coconut coir combines the air retention of perlite, with the water retention of vermiculite and it is a completely organic medium.

It can be reused and is biodegradable, relatively cheap and easy to obtain. It is also lightweight and easy to work with.

Another benefit of using coconut coir as a growing medium is that it offers plants protection against fungus and root diseases due to its anti-fungal properties. For all of these reasons, coconut coir is becoming one of the most popular growing mediums amongst hydroponic gardeners.



The advantage of perlite is that it has excellent oxygen retention and is very lightweight making it easy to transport.

It mixes well with other growing mediums. For example, you can mix it with soil and soil-free mixes to provide greater oxygenation for the plant roots.

Its lightweight properties make it easy to transport and apply. However, a disadvantage is that the hydroponic system can wash it away (the Ebb and Flow system, for example).

However, it works well with the wick-type hydroponic systems as perlite has good wicking action.

Expanded Clay Pellets

Clay Pellets

Lightweight Expanded Clay Aggregate (LECA) is a very loose medium with large grains.

The advantage of expanded clay pellets is that they remain pH-neutral and are reusable. This makes them cheaper and friendly to the environment.

Another advantage of clay pellets is the shape and internal structure of the pebbles which ensures good root aeration and drainage and helps prevent rotting.

The disadvantage is that expanded clay pellets are dusty, so they will need to be rinsed thoroughly before going into your hydroponic system.


Rockwool growing medium

Rockwool is made from molten rock that has been spun into long, glass-like fibers. You would typically buy Rockwool in the form of cubes or in a loose form.

The building construction industry uses Rockwool in wall insulation and it is popular amongst the commercial greenhouse industry.

The advantage of Rockwool is that you can use it for a wide variety of hydroponic systems since it easily absorbs water and drains well. It’s also completely sterile and non-toxic and makes for a good starting medium for seeds, cuttings, and small immature plants.

If your system constantly recirculates your nutrient solution, a fast draining medium such as Rockwool is ideal.

The disadvantage of Rockwool is that it is not biodegradable. Also, gardeners have complained of the substance irritating their skin.

Common Pea Gravel

Pea Gravel

Pea gravel is made up of stones less than an inch in size. Like expanded clay pellets they remain pH-neutral and are reusable.

Unlike expanded clay pellets, they are heavier. This can make transportation more difficult.

The advantage of using a heavy grow medium is that the medium does not get washed away with Ebb and Flow type systems.

Hydroponic Guide Sections

To learn more about other aspects of hydroponic gardening, see the following sections of our guide.