What is an air stone?

An aquarium air stone is sometimes also called an air (stone) bubbler or air (stone) diffuser. It is a device commonly used in aquariums to improve oxygen levels in the tank.

It often comes in the shape of a ball or stone (hence the name) and creates small bubbles by air being pushed through its pores or holes. Those air bubbles then dissolve oxygen into the aquarium water (also called aeration) ensuring high oxygen levels.

How does an air stone work?

In order to operate an air stone you also need to have an aquarium air pump. The aquarium air pump sucks in air and pushes it through a hose to the air stone.

The air stone itself doesn't really do anything - through its shape and small holes it simply ensures that the air that is being pumped into the aquarium comes in small bubbles.

This makes it easier for the water to absorb the oxygen that is being pumped into the tank than if it came directly out of a hose or in larger bubbles.

What are the benefits of using an air stone?

Using an air stone in your aquarium will increase the oxygen levels in the water and benefit your animals and bacteria.

Aquatic animals require at least 4-8 ppm oxygen in the aquarium water to survive. The higher the amount of oxygen in the water, the better. And while aquatic plants produce oxygen, it might not be enough for the needs of your animals. Especially if there isn't enough plant mass in the tank, you have a lot of animals or your animals need more oxygen than average.

Oxygen is also a necessary component in the Nitrogen Cycle. It helps the bacteria to convert ammonia into nitrite and nitrite into nitrate. Therefore it is already required when first putting a new tank together and cycling it before you put any animals in the tank.

Another situation where you may want to add extra oxygen to your aquarium is in the case of a bacteria bloom in a tank that contains aquatic animals. The bacteria bloom uses up a lot of oxygen, which could leave the aquatic animals with insufficient levels.

Can you use an air stone without a pump?

An air stone cannot be operated without a pump, because air needs to be actively pushed through the air stone. The air stone itself is a passive device that is only there to ensure the air is being split up into smaller bubbles.

The principle is similar to a shower head where water flows through little holes to make it split up into many small streams instead of coming out of the pipe in a single gush.

An air stone serves the same purpose, but for air instead of water.

If you are looking for a non-electric and noise-free solution you may want to take a look at Sochting Oxydator. This is a little container filled with the oxydator solution that you can put in your tank. Oxygen is then automatically being released into the aquarium water and dissolves immediately without any bubbles.

What are air stones made of?

Air stones can be made of plastics, acryl, ceramics or wood. Some float (needing a suction cup to fixate) while other sink to the ground.

A very simple and small round air stone from Eheim A very simple and small round air stone from Eheim

They come in many different shapes, either looking like a strip, or ball, a hose / curtain, cylinderor a disc. You can even buy air stones hidden in ornaments, like a volcano air stone with led lights looking like lava, a treasure chest that opens to release air or a sunken car wreck.

There are a lot of options to choose from and all serve the same purpose of increasing oxygen levels.

How to use air stones in fish tank?

In order to set up an air stone in your tank you simply need to connect it to an outlet of your air pump using a fitting hose.

An aquarium air stone valve that prevents water flowing back into the air pump An aquarium air stone valve that prevents water flowing back into the air pump

Pro tip: When using an air stone it is best to also install a check valve to make sure that no water from the tank flows into the air pump as this could potentially damage it. This is done by cutting the hose into two parts and putting the check valve in-between.

Then you need to blow air through both sides to check if it comes out at the other end or if you feel a resistance. If the air goes through you need to install the side you blew through on the pump and put the other side into the air stone.

Where to place air stone in aquarium?

After connecting your air stone to your air pump, simply place the air stone beneath the outlet flow in your tank. When the rising bubbles hit the outlet, they will be sucked into the flow ensuring that water with increased oxygen levels is distributed around the tank instead of being sucked out again immediately.

Can I place my air stone under gravel?

Yes, you can place an air stone under gravel in order to hide it from view and make it fit better into your aquascape. However, you need to make sure that your gravel layer isn't too densely packed for the air bubbles to come out of.

Another drawback to this method of placing the air stone might be that your bubbles could end up being bigger than intended. If the air stone is put under gravel the bubbles will have limited options of coming up through the gravel layer and will most likely combine into bigger bubbles throughout the process.

What is the most quiet air stone?

It's almost impossible to find a completely quiet air stone due to the way they work. As explained above, an air stream needs to be pushed through the material of the air stone to break it up into smaller bubbles. The air pump and the stream pouring into the water will naturally make some noise.

One way to make the noise more bearable would be to turn on the air pump only at night when you're sleeping (provided you don't sleep in the same room as the aquarium). This is recommended anyway, as your plants produce oxygen during the day and release CO2 in the evening. This makes the oxygen level in the water decrease in the evenings / at nights so that your animals will be thankful for a little help by your air stone.

If you're looking for a completely noise-less solution you might want to check out the Sochting Oxydator, which is a solution that works without an air pump.

Do I need an air stone in my aquarium?

If you have a planted tank and only small fish in your tank, you can probably do without adding any extra oxygen to your tank because the plants will produce enough of it.

But in case you don't have any live plants and are not using a sponge filter, you definitively need an air stone to provide the necessary oxygen levels to keep you aquatic animals healthy and safe. Bigger fish will also profit from an air stone as they need more oxygen.

In general you can tell you have a low oxygen level in you aquarium water when you see your aquatic animals grasping for air in the morning. Oxygen level naturally decrease during the night because the plants only produce oxygen during the day. At night plants release carbon dioxide and not oxygen to the aquarium water.

You can also use special oxygen meters or test kits to determined the amount of dissolved oxygen in your tank and make sure there is enough for your animals.

Air stone in planted tank?

You can put an air stone in a planted tank, especially to make sure the oxygen levels are kept up at night when your plants don't produce any oxygen.

An air stone is also advisable in planted tanks that house bigger fish like goldfish because they need more oxygen than e.g. cardinal tetra.

Which fish need an air stone?

If you have goldfish or other bigger and more active fish, you will most likely want to use an air stone in your tank to make sure they get enough oxygen - especially at night and in case you don't have that many plants in the tank.

Other aquatic animals that breathe exclusively via the aquarium water like axolotl will also most likely benefit from added oxygen.

Labyrinth fish like betta fish usually don't need added oxygen via an air stone because they can swim to the surface in order to breath fresh air in case they need more oxygen.

What does an aquarium air stone kit contain?

An complete aquarium air stone kit should always contain an

  • adjustable air pump (with rubber feet to minimize vibration / sound)
  • a hose (1 m / 3 ft)
  • a check valve (in case the pump is placed below water level)
  • a bubbler / diffuser
  • a suction cup (in case the diffuser floats)

If you can't find a complete kit that contains all of the above products, you can also order each item separately. Just make sure to check that they're compatible (e.g. the check valve should fit the hose).

What is the best air stone for my aquarium?

If you don't know what kind of air stone to by, here are some suggestions:

The cheapest air stone we could find was $5. It is a traditional cylinder air stone which has been the most commonly used type of air stone in the last couple of decades. Due to its size it is most suitable for small / nano tanks.

A disc-shaped acrylic air stone we like to use in our own tanks A disc-shaped acrylic air stone we like to use in our own tanks

Our favorite air stone is a bit more expensive at $26. It is fairly new to the market, but it looks very nice, makes a lot of small bubbles and is a transparent, which makes it very unobstrusive. You can choose from different sizes so that it suits your tank.

If you are looking for an air stone for bigger aquariums, they can cost around $70.

How to clean an air stone?

Do not use an oven or microwave for drying an air stone, it is not effective and might melt the plastic hose connection.

We recommend the following steps instead:

Step 1: Make or buy a solution

You can make your own cleaning solution by mixing chlorine (bought in the supermarket) with water. In case the air stone is very dirty you can mix it 1 to 2 (1 part chlorine with 2 parts water).

If it's not that very dirty you can also mix the solution 1 to 5 (1 part chlorine with 5 parts water). We recommend to start with the 1/5 solution.

Instead of using chlorine, you can also use a 100% vinegar or a 1 to 1 vinegar / water solution.

Another option would be using hydrogen peroxide 3%.

Step 2: Remove air stone from tank

Make sure to first remove the air hose from the air stone and then pull out the air stone.

Step 3: Soak air stone in solution

Place the air stone in the solution for 12-24 hours. Make sure the air stone is fully covered.

Step 4: Rinse air stone

After the air stone is has been soaked and is clean, you now need to rinse it under medium cold water. Rinse it thoroughly to make sure none of the cleaning solution is left as that would be harmful to aquatic animals.

Step 5: Dry air stone

You can either dry the air stone with a towel or plug it back into the hose and let it dry by air flowing through it.

When the air stone is fully dry, place it (fully connected) back into your tank.

In case you don't feel comfortable with using a chemical solution, you can also boil the air stone for 5 - 10 minutes and then let it dry. But do not boil the air stone when it's made from acrylic!