A question that I often see asked in forums and on Facebook groups is “do I need an air pump?” This question often results in a huge debate from people with varying views. Some say that they are essential and others feel that their only purpose is to produce pretty bubbles that look pleasing to the eye. In this blog we will take a look at the effectiveness and importance of these devices. (Skip to the bottom to see how a lack of oxygen recently killed 11 of my fish!)
Do they add oxygen to the water?
Yes and no. The bubbles themselves pass too quickly through the water to actually dissolve any significant amount of oxygen into the water. The largest gas exchange happens at the surface of the aquarium. Even without any water movement or bubbles, oxygen will be absorbed into water through the surface. This exchange happens a lot more efficiently if the surface tension of the water is broken by either a filter outlet creating ripples or by bubbles bursting. These ripples also significantly increase the surface area of the water, further aiding the gas exchange.
Another factor that can affect gas exchange is if an oil film forms on the surface. By breaking the surface, we can prevent this film from sealing the water from the surrounding air. Bubbles popping are far more effective than ripples from a filter as they actually blow this oily substance right off of the surface.
Do you actually need an aquarium air pump?
We have already learnt that they are definitely beneficial but are they actually necessary? In most cases, I would say that yes, they should be used. The chances are that you will be fine just aiming the output of a filter at the surface but why take the chance? Filters can clog causing reduced flow or even stop working completely. An air pump is a relatively cheap and efficient insurance policy. Also some experiments have been done which prove that an air pump coupled with an air stone is more efficient at oxygenating water than a filter breaking the surface.
How do air pumps work?
Most air pumps on the market are diaphragm pumps. Imagine a tiny pair of bellows being opened and closed very rapidly. This air is then forced along an airline into your aquarium where it gets forced through an air stone which creates tiny bubbles.
Check valve (Only required if the air pump will be situated below the water line e.g. in the cabinet under the aquarium)
You may also choose to add air operated decorations or a sponge filter. The advantage of a sponge filter is that it adds a backup form of filtration that reduces the negative effect if your main filter fails whilst also oxygenating the water.
How to reduce the noise of aquarium air pumps
Lots of people complain that air pumps create too much noise. The noise can come from a few different places. Firstly, cheap air pumps can rattle. It’s worth investing a little extra to buy a quality pump. Even good quality air pumps vibrate so making sure they’re not touching anything will reduce noise. You can also sit the pump on a piece of sponge or a folded cloth to help reduce noise even further.
Noise can also come from PVC airline touching a wall or the cabinet. This is due to the fact that PVC is a relatively hard substance which transmits vibration very effectively. An easy fix for this is to use silicone airline tubing which absorbs the vibration.
Finally, the air stone itself can make some noise. There’s no need to have so much air coming from the air stone that it creates the effect of boiling water. Most air pumps come with an integrated dial that allows you to reduce airflow. You can also buy inline air valves to control the flow. It also helps to have the air stone away from the glass.
My personal experience of a pump failing.
I recently had a failure which resulted in the death of 11 fish. The tank in question is a heavily stocked 6ft, 600 litre aquarium. It is filtered by a Fluval FX6 filter with the output aiming at the surface. It also had a large air pump powering 2 separate air stones. With all of this water movement, I was never concerned about lack of oxygen in the water.
That was until one morning, when I walked into the room I could hear a hissing sound and saw all of my fish at the surface gasping for air. When I looked closer I saw countless dead fish lying on the substrate.
It turned out that an airline had popped off of a check valve, meaning that no air was making it into the tank.
Thankfully I was able to save the remaining fish and I have since changed the single large air pump for two smaller ones. They each run their own air stone meaning that if one fails, I’ll still have one running plus the filter breaking the water surface.
This fix would’ve been so simple to implement before it became a big problem but I fell victim to complacency. I really highlighted the importance of having backups wherever possible.
I hope that this blog can help others avoid having the same problem!