Should You Use Air Stones in Hydroponics? Why?(Choose & Clean!)
Is it necessary to use air stones in my hydroponic system? I had the same question back then when I started my hydroponic journey.
Air stones are essential in hydroponics as they facilitate oxygenation, root integrity, and disease prevention. Air stone should be chosen based on jetting volume, dimensions, required pump wattage, and hydroponic reservoir size.
One of my favorite things about air stones is the variety of shapes available! But are they all suitable for any hydroponic system? Or are they purely for aesthetic reasons? Continue reading to find out the answer!
1. Oxygenation of Hydroponic Solution
Air stones elevate dissolved oxygen levels by producing bubbles in the hydroponic water. More bubbles in a nutrient reservoir equate to more area for roots to facilitate gas exchange.
To start this conversation, let me introduce you to dissolved oxygen.
Dissolved oxygen is just the amount of oxygen in the hydroponic solution in its dissolved form. (It is not rocket science, it is what it is!) But how is it important in hydroponics? Here is the principle.
When the concentration of dissolved oxygen reaches the maximum of its water solubility, the gas particles gather and form bubbles in the water.
There is more space for our hydroponic plant’s roots to breathe when there are more bubbles created in a hydroponic solution. Your hydroponic roots, believe it or not, also breathe! And, like us, they require spaces for oxygen to enter their roots.
This benefit can be provided by the air stones!
How Do Air Stones Work?
Air stones are paired with an air pump and hose to produce bubbles. The air pump generates air pressure, which is transported to the hose and released as bubbles through the airstones. These tiny bubbles are filled with oxygen that gives the hydroponic plants the supply of oxygen it needs to power biological processes.
Each gallon of water must be provided with at least 0.5 liters/minute of airflow. This information can be seen either in the package of air stones or air pumps.
So where should you put your air stone? The quick answer is at the bottom of your hydroponic reservoir where it will be closer to the plants’ roots.
Here are some hydroponic gardening scenarios summarized in a table to help you decide how many air stones to buy and where to put them.
| Hydroponic System Type | Air Stone Type | Recommended Quantity of Air Stones | Optimal Position in the Hydroponic Reservoir |
|---|---|---|---|
| 4-liter Deep Water Culture (DWC) Bucket | Cylinder, Cuboid (< 1” diameter) | 1 | Bottom middle just below the roots |
| 12-liter Deep Water Culture (DWC) Bucket | Cylinder, Cuboid (< 1” diameter) | 3 | Distributed in 3 sides of the bucket |
| 15-liter Rectangular Deep Water Culture Box | Cylinder, Cuboid (< 1” diameter) | 4 | Distributed in each side of the rectangular reservoir just above the plants’ roots |
| 4-liter Deep Water Culture (DWC) Bucket | Disc (1-2” diameter) Ball (2” in diameter) | 1 (will produce too many bubbles) | Bottom middle just below the roots |
| 12-liter Deep Water Culture (DWC) Bucket | Disc (1-2” diameter) Ball (2” in diameter) Bar (8” in length) | 1 | Bottom middle just below the roots |
| 15-liter Rectangular Deep Water Culture Box | Disc (1-2” diameter) Ball (2” in diameter Bar (8”-10” in length) | 1 | Bottom middle just below the roots |
Explore further: Is it possible to have too many bubbles in hydroponics?
2. Assurance of Root Integrity
The root integrity of hydroponic plants is ensured when there is an adequate supply of bubbles produced by airstones. Stagnant and deoxygenated water will lead to the development of root slime, which can inhibit the absorption of oxygen and nutrients by the roots.
Two factors affect the development of root slime, which is one of the greatest enemies of hydroponic plants—water movement and oxygen levels.
1. Water Movement
Have you ever left water in a container for a long time? As a gardener, I’ve done this numerous times, particularly when watering my plants. When I leave water in my sprinkler for several days, slime forms on the surface of the watering can.
This also occurs in hydroponics if the water is left stagnant. This is because brown algae, the causative agent of root slime, finds this condition to be a favorable environment for growth.
Fortunately, the air stone generates air pressure, which causes movement in the hydroponic water.
2. Oxygen Levels
When the oxygen levels in a hydroponic solution is too low, root fungus such as Phytophthora also develops.
This fungus grows in environments with water and poor oxygen concentration. It dominates the roots as it produces slime. Thus, it is critical to maintain ample oxygen levels in a hydroponic solution.
Learn more about this in our article on the causes of hydroponic root rot.
3. Prevention of Waterborne Diseases
Low oxygen levels in hydroponics are also critical in plant disease development, specifically, fungi and bacteria. Air stones prevent their growth by enriching the hydroponic solution with oxygen.
Here are common waterborne diseases affecting hydroponic plants:
- Phytophthora Rot (common in all hydroponic plants)
- Fusarium Wilt (tomatoes)
- Bacterial Soft Rot (tomatoes, eggplants)
- Pythium Rot (lettuce)
Read more about this in our article on reasons of root rot (with solutions).
How to Choose an Airstone (4 Factors)
To choose an airstone, it is best to consider the following factors:
- Jetting Volume (Airflow Produced in Liters/Minute)
- Dimensions
- Pump Wattage Needed
- Size of Hydroponic Reservoir
When deciding which air stone is best for you, compatibility is the most important factor to consider. Make sure your air stone is compatible with both your air pump and your hydroponic system.
Once these elements are coordinated, you may have a functional hydroponic system that will produce a bountiful harvest!
Discover more about this in our article on best air stones for hydroponics.
The Only Hydroponic System That Requires Air Stones
Deep water culture (DWC) is the only hydroponic system that requires the use of air stones. This is because the roots in this specific system are completely submerged in water 24/7. Under this condition, roots are deprived of oxygen, thus aeration with the use of an air pump and air stone is advised.
This section might have broken an established notion for you as a gardener. But you read that right: Not all hydroponic systems require air stones and even air pumps!
So, how does deep water culture work?
Why? Let us have a quick recall of the past sections.
Air stones in hydroponics give the roots more space to breathe, right? So the reason why we need aeration is for the roots to have space that will facilitate gas exchange. Ample space.
Other hydroponic systems such as nutrient film technique, ebb and flow systems, and aeroponics, already have that space! This is because in these particular systems, the roots are not immersed completely in water.
More specifically:
- Nutrient Film Technique: Only the bottom portion of the roots has direct contact with the circulating nutrient water.
- Ebb and Flow System: Plants are temporarily flooded with nutrient water then drained after some time.
- Aeroponics: The roots are only misted with the nutrient water using a timed spray.
Air Stone Classifications: Based on Material & Shape
Air stones are classified based on the material used to make them as well as their shape.
2 Materials Used to Make Airstones
Aluminum oxide and silica are two common materials that are used to manufacture air stones for hydroponic gardening.
1. Aluminum Oxide
Aluminum oxide is the most common material used for airstones available on the market. They are durable and can last for 3 to 5 years with regular cleaning.
The bubble sizes they create are not super fine, as they range from 2 to 4 millimeters in diameter. However, this is normal for airstones.
The product below is an example of an aluminum oxide-based air stone. You can get it on Amazon!
If you want super fine bubbles, check out our article on the best air diffusers for hydroponics.
2. Silica
Silica-based airstones are cheaper but are not as durable as those manufactured from aluminum oxide. Since it is made of silica sand, it is unreactive to most chemicals, but it can alter the pH of your hydroponic nutrient solution because of its alkaline nature.
The airstone below which is available on Amazon is an example of this type.
5 Shapes of Air Stones Available in the Market
Based on the shape, air stones are available in cylinder, bar, disc, ball, and cuboid.
1. Cylinder
Cylinders are the most common shape of air stones and can work well with any hydroponic reservoir. With its dimension range of 0.6” to 2” in diameter, it can give an airflow of 0.8 to 5 liters of air per minute.
These air stones best operate with air pumps having 2 to 8 watts, depending on their size.
The bigger the hydroponic air stone, the more power wattage is needed.
2. Bar
Bar air stones are fit for rectangular hydroponic reservoirs. This is because they are longer in size, thus they can distribute the bubbles well throughout the reservoir.
They may range from 4.5” to 12” in length and operate with 2 to 10W air pumps. Furthermore, their air flow rates range from 1.3 to 15 liters of air per minute.
3. Disc
Disc type is a small but powerful air stone option. This type may measure 1.5 to 4” in diameter, making it perfect for deep water culture buckets.
Air stones of this shape and size are best paired with a 2 to 4 watts air pump to deliver an airflow rate of 2 to 12 liters of air per minute.
4. Ball
The ball-type air stone is another good option for hydroponic buckets because of its larger size, compared to the cylinder and cuboid variants.
Below, you will find a ball-shaped air stone that is 2” in diameter. It gives an airflow of around 5 liters of air per minute if paired with a 4 to 8 watts air pump.
5. Cuboid
The cuboid-type air stone is less popular as it is very similar to the cylinder type.
The product below measures 1.2” in height, gives 0.8 liters per minute of airflow and works best with a 2-watt air pump. This is also used for deep water culture buckets, especially smaller ones.
3 Ways to Clean Air Stones for Hydroponics
Cleaning a hydroponic air stone regularly and properly reduces the noise it produces and extends its lifespan. It can be cleaned by just soaking it in hydrogen peroxide, bleach, or vinegar.
1. Hydrogen Peroxide
- Dissolve 2-3 teaspoons of hydrogen peroxide per gallon of water.
- Soak the air stones in the hydrogen peroxide solution overnight.
- Finally, thoroughly rinse them with clean water before reintroducing them into your hydroponic system.
2. Vinegar (Organic!)
- Dilute 1 part of vinegar with 2 parts of water.
- Soak the air stones in the vinegar solution overnight.
- Rinse them well using distilled water.
- Let the air stone dry.
3. Bleach
- Mix 1 part of bleach into 3 parts of water.
- Immerse the air stone in the bleach solution for 24 hours (or longer if it’s really clogged!).
- Rinse them well with water.
- Soak for another 12 hours only in water. (this step will weaken the strong disinfecting effect of bleach)
- Rinse for the second time.
Compare disinfectants in our article on hydrogen peroxide vs bleach.
FAQs
What is the difference between an air stone and an air diffuser?
An air stone and air diffuser mainly differ in terms of the size of bubbles they produce. Air stones produce bigger bubbles with a diameter of 2 to 4 millimeters, whereas air diffusers produce finer bubbles with <0.5 to 1 millimeter in diameter.
Is there a similarity between an air stone and an air diffuser?
Both air stones and air diffusers work to increase the dissolved oxygen levels in the hydroponic water reservoir. They are both helpful in maintaining the health of the roots and preventing the spread of fungal and bacterial diseases in the hydroponic system.
Do air stones affect pH?
Air stones can affect the pH of the nutrient solution. To be more specific, air stones made from alkaline materials, such as silica, can raise the pH of the hydroponic solution. In the case of aluminum oxide, which can react with both acids and base, it can raise the pH if the current pH is low, and vice versa.
What is the average lifespan of air stones?
High quality air stones can last up to 2 to 3 years with proper cleaning every six weeks. Sanitation, checking for clogging, and disinfection of air stones play an important role in prolonging their efficiency and reliability.
Summary of 3 Roles of Hydroponic Air Stones
Hydroponic air stones are used to increase dissolved oxygen levels, ensure good root growth, and hinder the development of plant diseases. For optimum efficiency, it is critical to make sure of the compatibility of the airstone with the air pump and hydroponic reservoir.
The only hydroponic system that requires the use of airstones is deep water culture. This is because the roots in this system are completely and continuously immersed in water. As a result, they require aeration to respire and facilitate biological processes for growth and development.
Air stones differ in terms of material (aluminum oxide and silica) and shape (cylinder, bar, disc, ball, and cuboid). Cleaning can be accomplished by simply soaking the airstone in hydrogen peroxide, vinegar, or bleach for a while, depending on the degree of clogging.
Sources
- “Fungal diseases in vegetable crops” by N/A in AUSVEG
- “Growth of bubbles in liquid” by Smirnov, B.M. and Berry, R.S. in Chemistry Central Journal
- “Susceptibility to water-borne plant diseases of hydroponic vs. aquaponics systems” by Cáceres, G.S. et al. in Science Direct
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