When you’re setting up a Deep Water Culture hydroponic tank, you need a good air stone.
An air stone is a critical component to successful hydroponic growing since it’s responsible for introducing usable oxygen to your plants’ roots. Air stones come in various shapes and air flow capacities, so choosing one that’s right for your system is key.
This article will review 7 of the best air stones for hydroponics, with options for home set-ups of all sizes.
Plus, you’ll learn about the science behind them, the best size for your needs and general guidelines for use and maintenance.
So let’s jump into the details of hydroponics air stones!
1. Hydrofarm Active Aqua ASCM Air Stone Cylinder
Hydrofarm offers this air stone in three different sizes:
- 1.4 x 1.7 inches
- 2 x 2 inches (featured here)
- 2 x 4 inches
We’re highlighting the medium size here because it’s versatile enough to be used in everything from a 5-gallon bucket to a 20-gallon drum.
One great thing about this stone is that it’s heavy enough to sink to the bottom of your container and stay there. This helps cut down on your time reaching into the tank to fix your air stone while also ensuring maximum water circulation and oxygenation.
Also, the micropores on the stone churn out lots of small, readily absorbable bubbles. This is a workhorse that definitely gets the job done!
NOTE: This stone does need a fairly powerful pump to produce the correct volume of bubbles. A pump with at least 240 gallons per hour output should be fine, like this 6-watt one, also from Hydrofarm.
2. CNZ Fish Tank Air Bubble 2-Piece Air Stone Bars
The bar is kind of the “classic shape” for air stones, and they work well in Deep Water Culture. Their elongated shape offers plenty of great bubble coverage and aeration, especially for larger rectangular reservoirs.
These bar air stones come in a two-pack and have five different lengths to choose from:
- 8-inch (featured here)
You can split them up between different containers, or place both air stones in one reservoir for maximum bubbles.
So whatever the dimensions of your reservoir, you should be able to find a size that’s the perfect fit.
One downside is that the long, thin shape can have a tendency to float, and these are pretty lightweight to begin with. You may need to add suction cups on the airline tubing to keep your air stone where you want it.
3. Pawfly 4-Inch Air Stone Bubble
This half-dome shaped air stone puts out a large volume of small, consistent bubbles at 20 liters per minute, making it one of the more powerful air stones on this list.
Its hemispherical shape has no edges or corners to get in the way, so you get a large amount of fine, uniformly-sized bubbles. This is ideal because small bubbles make it easier for your plants’ roots to absorb the oxygen.
On these bubble-shaped air stones, the connection for the tubing to the air pump is directly on top instead of on the side as it is with disk-shaped air stones. This eliminates any chance of a kinked line obstructing your airflow.
It also makes setup and maintenance quite a bit easier, especially if you use it in a narrow five-gallon bucket DWC.
If you prefer, Pawfly also offers this stone in a 2-pack.
One thing to note: This stone requires a long pre-soak. Pawfly recommends soaking for 3 hours, but users report much better performance with soaking 6-12 hours at the very least.
4. VIVOSUN 5 Inch Air Stone Disc with Shell
Another great option for shallow reservoirs is Vivosun’s disc-shaped air stone. You’ve got three size options to choose from:
- 5-inch (featured here)
With its low profile and three available sizes, this is one of the best air stones for DWC because it can fit almost any setup.
At 14 liters of air per minute, it also produces a steady flow of small, fine bubbles, which is ideal for optimally oxygenating water.
Both the 4-inch and 5-inch options stand 0.8 inches tall, and we recommend them for reservoirs that hold 5 gallons to 15 gallons.
Just be aware that the 8-inch size option is definitely a beast. It stands 1.5 inches tall, and you’ll need an air pump with at least a 16-watt output and larger 8 mm air line tubing.
Unless you’re working with a large-scale reservoir, it’s probably more power than you need.
5. AQUANEAT 2 Pack Air Stone
With two stones in a pack, and three sizes to choose from, these air stones from Aquaneat offer great value.
Two stones mean that you can set up two separate DWC reservoirs. And three size options allow you to customize according to the volume of your reservoir.
Your size choices are:
- 2 x 2 inches
- 4 x 2 inches (featured here)
- 6 x 2 inches
The smallest option (2 x 2 inches) is ideal for a 5-gallon bucket to 10-gallon containers. The medium-sized (4 x 2) air stone is excellent for containers that are 20 gallons or more.
Both the small and medium size options are great for home hydro systems. But the biggest size (6 x 2) is best-suited for large-scale set-ups or commercial growing.
These air stones pump out a ton of bubbles, and the top-end hose attachment means that your tubing won’t get kinked up against the side of your reservoir.
Reviews also mention that these are heavy and sturdy, so they’ll keep themselves anchored at the bottom of your DWC with no problem.
One thing to be aware of: Don’t skimp on the pre-soaking time. Some users have run into trouble with the stones not working properly if they’re not soaked long enough, so plan for some extra set-up time.
6. Pawfly 4-Inch Air Stone Disk
Pawfly’s 4-inch air stone is a flat round disk that rests on the bottom of the reservoir and releases a steady stream of small-diameter bubbles.
Since disk-shaped air stones have a flat, wide design, they may try to float away if they don’t have a lot of weight to hold them down. So one nice feature is the addition of three small suction cups already on the stone’s outer rim.
This makes it easy to stick your air stone firmly to the bottom of your hydroponic tank.
Pumping out a respectable 12 liters per minute of air, this air stone is totally adequate for small-to-medium sized DWC reservoirs of about 10 gallons or less.
7. Wenshall Small Round Air Stones
Last but not least, Wenshall’s four-pack of air stones are small but mighty.
Each stone generates 2 liters of airflow per minute. They put out a ton of bubbles for their size while still being heavy enough to sink to the bottom and stay there. No small feat for such a small piece!
If you’re just starting out with air stone hydroponics, typically DWC, these can be a great choice for you. They fit easily inside smaller reservoirs, and they have a low price point.
You can also use two together for more aeration or for larger reservoirs.
But keep in mind that the minimum airflow should be about 1 LPM for each gallon of water. So these stones aren’t ideal for set-ups over 8 gallons in volume, even if you use all four stones together.
What Does an Air Stone Do?
Simply put, an air stone introduces oxygen into water.
Air stones release a steady stream of fine bubbles at the bottom of your reservoir. As the bubbles rise to the water surface, they pass through the plant’s root web, where your plant absorbs oxygen and iniates cellular respiration.
This dissolved oxygen also increases nutrient uptake from the hydroponic solution to the roots. In fact, a lack of oxygen actively prevents your plant from taking up the nutrients they need, even if you create the most nutrient-rich water possible!
Good oxygenation is so important that many hydroponic growers also add hydrogen peroxide (H202) to their systems. As it breaks down, H202 releases oxygen (and does a lot of other great things in the process!)
Bonus: If you want to know more, we’ve covered this topic in detail in our post on H202 for hydroponics.
But air stones can’t do the job of oxygenating your hydroponic tank all by themselves. You also need an air pump to generate the airflow that passes through the air stone.
The two pieces working together produce the oxygenation that makes for such high yields in hydroponic growing. With enough oxygen to the roots, the plant grows faster and processes nutrients much more efficiently.
RELATED: We put together a post on 7 of our favorite air pumps to pair with your air stone. Stop by to pick up some helpful tips and suggestions!
Types of Air Stones
Air stones come in many different shapes and sizes, some of which are better suited to hydroponics than others.
The best air stones for hydroponics are:
- Bubble (or hemisphere)
You should choose a size and shape of air stone based on the size and shape of your reservoir.
A bar-shaped air stone, for example, will work great in a large rectangular reservoir, but would be a poor fit for a round five-gallon bucket.
A disk would create plenty of bubbles for a bucket, but might not create enough coverage for a larger reservoir.
Unless they’re pre-weighted, some cylinder stones tend to topple over and roll around more easily than other shapes. The ones we’ve covered here are already on the heavy side, so they should stay put.
But if you prefer a different brand that starts to float or move, you can use a suction cup on the airline tubing to secure it. This suction cup multi-pack from Pawfly is affordable and will last you a long time.
Is an Air Stone the Same Thing as an Air Diffuser?
Air stones and air diffusers have the same purpose: To oxygenate water in a hydroponic system. But they are different tools.
An air stone is essentially a very porous rock through which the air pump forces oxygen.
They’re inexpensive and effective for aquariums and smaller setups. But they tend to be less powerful and less consistent the more you try to scale up with them.
Air diffusers are made of flexible tubing that can be shaped to fit whatever reservoir they’re destined for.
They distribute bubbles very evenly throughout the reservoir and are less prone to clogging or breaking than air stones. They are favored by more advanced hydroponic gardeners and commercial hydroponics growers.
RELATED: Ever wondered if hydroponics and aquaponics are just two names for the same thing?
Learn more in our post outlining the key differences between hydroponics and aquaponics.
How Big of an Air Stone Do You Need?
Generally speaking, the more bubbles, the better.
Conversely, while you can’t have too much oxygen in the water, you can have a bubble stream that is too powerful. You want to aerate the roots, not stress them out by subjecting them to a strong current.
The bare minimum for an air stone in hydroponics should be 1 liter per minute of airflow for each gallon of water in your system.
So for a 5-gallon bucket, you’ll need 5 LPM of airflow at the very least, for a 15-gallon reservoir, you’d need 15 LPM, and so on.
This is when buying a pack of multiple air stones can be really helpful. If one isn’t enough, you can easily add one or more to your reservoir without having to choose and purchase another, larger stone.
You can also use air valves, like these small plastic ones. A valve allows you to easily control and adjust the bubble rate of your air stone.
Should You Pre-Soak an Air Stone?
Yes, all air stones need to be soaked prior to use.
While some manufacturers say that their stones need soaking for as little as one hour, users seem to get better results from their air stones after soaking them for at least six hours and up to a day.
You’ll also get the best airflow from your air stones if you clean them each time you clean your hydroponic tank. The recommended cleaning schedule is typically once weekly or bi-weekly.
With a bristle brush or old toothbrush, thoroughly scrub the outside of the air stone and rinse it well several times in clean water. Skip the soap, since that can be hard to completely wash away.
You can also do this whenever you feel that the volume of bubbles released by your air stone has lessened, as clogging is often a culprit in that scenario.
Do All Hydroponic Systems Need an Air Stone?
Deep Water Culture (DWC) is the only hydroponic system where you absolutely must have an air stone and pump. Other systems, like Ebb and Flow, Nutrient Film Technique and drip systems, use other methods of getting proper oxygen to your plant’s roots.
All of these growing methods are called active systems, and they all rely on electrical power to circulate water and expose plants to oxygen.
But there are passive methods of hydroponic growing that don’t require any electricity or airflow (and thus, no air stone).
Passive hydroponic systems are all variations on the central Kratky method. They involve suspending the plant roots over a nutrient-rich water solution and allowing the plant to simply absorb the water as it grows.
These systems accommodate plants with fast growth patterns and limited or no fruit production. But that doesn’t mean that you don’t still have a great variety of plants to choose from! We put together a list of Kratky-friendly plants, so check it out to get some ideas!
Also, our post on Mason jar hydroponics offers a great example of what passive hydroponics looks like on a tiny scale.
Frequently Asked Questions about Air Stones for Hydroponics
Air stones are a valuable and easy addition to home hydroponic systems that can take your setup to the next level.
Although there are a lot of hydroponics air stones to choose from, honestly, it’s hard to make a bad choice. The introduction of even a little oxygen to a hydroponics system will net you big results in your harvests.
Pick the best shape and size for your reservoir, and you’ll be reaping the benefits in your next harvest!
Do you have any more questions about air stones? Are there any other model you’d add to the list?
Let us know in the comments!