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Deep Water Culture (DCW) hydroponics is a great way to grow leafy greens and vegetables at home. But there is one important element that often gets overlooked: air pumps. An air pump is critical for DWC hydroponics, providing oxygen for your plant’s root system and for circulating nutrient-rich water throughout the reservoir. Getting the right size air pump for your system is therefore a critical success factor.
As a general rule, you should aim for a minimum of 1 watt per gallon of nutrient solution. For example, if your DWC hydroponics system has a 3-gallon (13.6 litres) reservoir you should use a 3+ watt air pump. This is generally considered sufficient by most hydroponics growers. The air pump should also have a flow rate of around 0.2 gallons (1 litre) of air per minute for every 0.9 gallons (4 litres) of nutrient solution.
In this article, I’ll go over all the factors to consider before choosing an air pump for your DWC hydroponics set-up. We’ll also explore why an air pump is so important and how different kinds can affect your plant’s growth in different ways. Let’s get on with it!
Hydroponics air pumps: The basics
An air pump is an integral part of any DWC (Deep Water Culture) hydroponics system. Its primary purpose is to aerate the nutrient solution contained within the reservoir and provide oxygen to the plant’s root system. If the roots do not receive enough oxygen in DWC hydroponics then can suffer from oxygen deprivation and eventually die.
Why is oxygen so important in DWC?
Oxygen is vital for all plants to thrive. It’s especially important in DWC hydroponics because the root system is permanently submerged within the nutrient solution. Without oxygen, the plant’s roots cannot efficiently absorb nutrients, leading to deficiencies and stunted growth. A lack of oxygen is also known to cause root rot and other diseases which can lead to the plant’s death if not treated quickly.
Air pumps and air stones
Most air pumps are typically used in conjunction with an air stone (sometimes referred to as a ‘bubbler’). An air stone is a lightweight stone (or brick veneer) that is placed into the nutrient solution and connected to the air pump via a hose.
When air passes through the stone it creates tiny bubbles that rise towards the surface and filter through the plant’s roots. These bubbles further help to oxygenate the water which benefits the plants.
Calculating the best air pump size for your DWC hydroponics system
Calculating the size of the air pump you need is relatively simple if you stick to a couple of universal rules. Both should be true to consider the pump size correct for your DWC hydroponics system.
Pump Power vs. Reservoir Size
The first equation you need to balance is the power of the air pump vs. the total volume of the reservoir. As a general rule, the power (watts) of the air pump should be equal to the total number of gallons in the reservoir. For example, a 5-gallon reservoir will need a minimum of a 5-watt air pump.
Air Pump Size (watts) = Total Volume of the Reservoir (gallons)
Pump Capacity vs. Reservoir Size
The next rule of thumb helps to determine the capacity of the air pump for your DWC system. As a general rule, the air pump should have a flow rate of 1 litre of air per minute for every 4 litres of nutrient solution in the reservoir.
Reservoir Capacity (litres) / 4 = Pump Capacity (litres per minute)
Let’s take the Oxypot XL DWC System – 70 Litre Reservoir as an example. To work out the necessary pump capacity, in this case, you could perform the following calculation: 70/4 = 17.5. So, in this example, you would need an air pump with the capacity for at least 17.5 litres of air per minute.
Taking into consideration the power you would also need a pump with a capacity of around 15 watts.
The Hailea ACO Series 960L/hr 18-watt capacity pump in this case would be the closest match. But an air pump with greater capacity than this would work well.
Other important factors to consider when making your purchase
In addition to the air pumps power, there are several other factors that you should consider before making a purchase:
- Flow rate: Consider the flow rate of the pump and make sure that it is capable of providing the desired effects. The pump should be able to provide around 0.2 gallons (1 litre) of air for every 0.9 gallons (4 litres) of nutrient solution.
- Noise level: Consider where your system is positioned and whether or not you need an air pump that operates with low noise levels. Diaphragm pumps are generally considered quieter than piston pumps.
- Adjustability: Some of the best air pumps allow you to adjust the airflow making them much more flexible options than those with one, consistent flow rate.
- Durability: Hydroponics can be a messy business. It’s important to choose an air pump which is durable and can last a long time. Make sure to read the reviews.
- Cost: Make sure that you consider both the cost of the air pump and any ongoing energy costs to run to ensure it’s within your budget.
The best air pumps for DWC hydroponics
There are a tonne of air pumps on the market suitable for DWC hydroponics. Sticking to the two universal rules outlined above will help. However, I’ve listed a few products below that are widely considered solid options for their capacity, power, durability and cost (as of 2022).
Best all-around air pump for DWC hydroponics – General Hydroponics HGC728040 Dual Diaphragm Air Pump 320 GPH 4 Outlet
This is a great pump for most hobbyist DWC setups. It has 4 outlets and a capacity of around 20 litres per minute (44 gallons).
Low output air pump – Hydrofarm Active Aqua Commercial Air Pump, 4 Outlets, 6W, 15 L/min
A small 3W, 15L/min capacity air pump is great for smaller DWC systems and hobbyist hydroponics growers starting their first system. Runs pretty quietly and is good value.
Medium capacity air pump – EcoPlus ECOair3 Commercial Grade Air Pump 1030 GPH – 35 Watt Single Outlet
Offers reliable performance and comes with a pump, brass output nozzle, adjustable air manifold, and 1/4-inch tubing. It also has a one-year warranty.
Can you have too much air for DWC hydroponics?
While air and oxygen are important for plant growth and health it is possible to overdo it. Too much oxygen can cause stunted roots and other issues that may have a negative effect on your crop. This is because an oxygen-rich environment negates the root’s need to grow larger.
Stunted roots often lead to stunted plants with less biomass. It’s important to monitor the oxygen levels in the nutrient solution to make sure that they are not too high.
How long should you run the air pump in DWC hydroponics?
In DWC hydroponics the general consensus amongst growers is that the air pump should run continuously for 24 hours per day. This ensures sufficient aeration of the nutrient solution and that the submerged plant’s root systems absorb enough oxygen.
For other types of hydroponics systems, the air pump run time can vary. I’ve written an entire article about how long you should run your air pump in hydroponics. Feel free to read it.
What are the main benefits of an air pump for DWC hydroponics?
Adding a hydroponic air pump to your system has a number of benefits that reach beyond simply aerating the nutrient solution and improving a plant’s oxygen intake. This is why some growers choose to add an air pump to systems other than DWC, even if it isn’t strictly required for the plant’s survival.
- Increased oxygen levels: An air pump helps to increase oxygen levels in the nutrient solution which is essential for the health and growth of your plants.
- Improved nutrient uptake: Increased oxygen within the nutrient solution can improve your plants’ ability to absorb nutrients leading to stronger and faster growth.
- Prevention of algae growth: Algae love low-oxygen environments. Keeping oxygen levels high with an air pump helps to prevent algae growth.
- Better root health: More oxygen in the nutrient solution can lead to improved root health which in turn creates stronger, healthier plants.
- Enhanced root rot: Root rot is a common problem in hydroponics, particularly in DWC. Higher oxygen levels can help to prevent this.
- Improved circulation: An air pump can help to circulate water and nutrients throughout the nutrient solution which helps to prevent a harmful build-up of algae, bacteria and fungi.
Final thoughts
Choosing the right size air pump for your DWC hydroponics set-up can be daunting at first but with the knowledge you’ve gained in this article, it should be a straightforward process. Ensuring the air pump’s power is at least 1 watt per gallon and has a flow rate of around 0.2 gallons (1 litre) of air for every 0.9 gallons (4 litres) of nutrient solution you’re almost set.
Carefully consider how you intend to use the air pump for your system, and how your system might change and grow over time. Consider the number of air stones you need and the oxygen requirement of your plants. Remember, it’s possible to provide too much oxygen, so make sure you measure this as much as possible.