It definitely isn’t the most exciting part of owning an aquarium…
In fact, surface agitation is often overlooked, especially by beginners.
But that doesn’t change the fact that surface agitation is important!
So today, I am going to teach you everything you need to know about it!
What is surface agitation?
Have you ever seen a puddle of water that is so calm, still and smooth that it looks like a mirror?
Yeah, like that…
Well, if you added nothing but water to your aquarium, that’s exactly what the surface would look like.
However, if you throw a stone or splash around in the puddle, the surface of the water would become rippled.
In aquariums, this movement of water on the surface of the tank is referred to as surface agitation.
It’s a boring and often forgotten aspect of aquariums, but surface agitation is important for most tanks.
Why is surface agitation so important?
The most compelling argument for surface agitation is self-explanatory…
It oxygenates your water!
As you are no doubt aware, the oxygen that your fish breath works its way down into your tank from the surface…
The bigger the surface area of the tank, the more oxygen can penetrate the water.
Now, ordinarily the water surface area is determined by the size of your aquarium.
A 4 ft x 2 ft aquarium, for example, has a lot more surface area than a small fish bowl.
When you agitate the surface water in your tank, the layer of water that is in contact with the air is constantly changing – the agitation increases the surface area of your tank, even though the physical dimensions of your aquarium are unchanged.
Surface agitation promotes gas exchange – the agitation increases the rate at which oxygen (O2) dissolves in water. It also increases the rate at which carbon dioxide (CO2) is released from the water.
The amount of oxygen in your aquarium plays a major role in determining how many fish you can keep in your tank.
You need enough oxygen to keep each fish alive! The more oxygen in the water, the more fish you can keep!
Surface agitation allows you to keep more fish in the same-size tank.
That’s a pretty convincing argument for surface agitation, huh?
Even if you are not planning on stocking any more fish, there is another added benefit of surface agitation…
It gets rid of that oily film that appears on the surface of still aquariums.
You know, that oil slick that begins to form?
Well, the reason it isn’t going anywhere is because there is no water movement.
Agitating the surface water will help break up the oily film.
Is there such a thing as too much surface agitation?
In most cases, the surface agitation caused by aquarium equipment won’t cause any problems.
However, there are two instances when strong surface movement actually works against you.
1. Your fish
It may surprise you to learn that some fish hate surface agitation or any other water movement.
One of those fish is the Betta splenden (Siamese fighting fish).
I know that many fish stores keep their betta in a tank with an air stone bubbling away, agitating the surface of the water. But this stresses the fish.
In their natural environment, betta live in rice paddies and marshes – water that is very still.
To keep your betta happy at home, you want to replicate the gentle water movement found in its natural habitat.
So, read up on the preferred water movement of your fish before adding any surface-agitating devices.
2. Planted tanks
Remember how I mentioned earlier that agitating the water also increases the rate at which CO2 exits the water?
Well, for planted tank owners who are injecting CO2 into the water, that isn’t necessarily a good thing – you want the CO2 to stay in the water, not leave it.
If you are injecting CO2 into your tank, you want to reduce agitation down to a gentle ripple – so that you are not wasting CO2.
How do you agitate the water in your aquarium?
So, you have decided you want to agitate the surface water of your aquarium.
Here are four simple devices that will do just that!
If your tank already has a filter set up, then you will most likely have everything you need to agitate the surface of your aquarium already.
Hang on back (HOB) filters and under gravel filters both have return lines that cause water movement at the surface of the aquarium, agitating the water.
For canister filters, you need to point the return up towards the surface of the water to agitate it.
Sponge filters use either an airstone or air line to operate. As the bubbles rise to the surface, they agitate the water.
2. Aquarium bubbler
Commonly used by beginners and owners of small tanks, aquarium bubblers offer an affordable means to agitate the surface of your tank.
Simply hook the bubbler up to an good aquarium air pump and insert it into your tank. The bubbler will produce hundreds of tiny little bubbles. As the bubbles rise, they churn the surface of the water.
Popular types of aquarium bubblers include airstones and bubble walls.
3. Power head
A powerhead is essentially a submersible pump that is placed inside your aquarium to boost the water movement.
Water is drawn in through the bottom of the unit and out the top. As the water flows from the return, it stirs the surface of the water.
Essentially a circulating fan, a wavemaker is positioned inside your tank and recreates the water movement of naturally occurring waves in the ocean.
By aiming the fan upwards, the wavemaker is more than capable of agitating the surface water.
5. Spray bar
In its simplest form, a spray bar is little more than a piece of pipe with holes in it.
A spray bar sits on your filter outlet and disperses the water evenly and gently across the surface of your aquarium.
6. Lily pipe
A lily pipe is a flower-shaped glass pipe that sits on the outflow of your aquarium filter.
As water flows through the pipe, it disperses water across the surface of your aquarium, agitating it. Lily pipes that are specifically designed to agitate the surface water are called poppy pipes.
It may not be the most exciting thing you will read about aquariums today, but surface agitation is an important part of fish keeping.
Do you agitate the surface of your aquarium? Let me know your preferred method in the comments below!
Ian Sterling, founder of Fishlab.com, began his aquarium journey over 30 years ago, driven by a deep fascination for fish and their diverse personalities. His website, Fishlab.com, is dedicated to making fishkeeping accessible and enjoyable, offering beginner-friendly guidance, expert insights, and a community for aquarists to connect and share experiences.