Some aquarium air pumps are quieter than others but they all make noise. All air pumps have moving parts inside, so naturally, the motor makes sounds. It is possible, however, to lessen the noises the pump makes through simple, quick fixes and easy maintenance tasks. This is important to remember, as too much noise is detrimental to the fish.
Keep Equipment Clean
When the air stones and those tiny plastic hoses get clogged up with algae, fish waste, old food and rotting plant matter, the pump's motor has to work harder to move the air through the pump and into the tank. This creates more noise as the motor runs faster and faster over time. If not dealt with, by cleaning the equipment, or replacing clogged equipment with clean, the motor could eventually burn out.
Keep the Pump Raised Above the Water Level
The machine works against gravity to pump air upward, while the water tries to force its way down the hose and into the machine. This makes the pump work harder to keep the pressure stabilized. Keeping the pump positioned higher than the water level helps to maintain correct water pressure on the hose and keeps the sound down to a minimum because gravity is now working with the pump instead of against it.
Use a Sound Dampening Surface
Setting the air pump on a hard, dense surface that doesn't add to the vibrations will help absorb some of the sound. Placing the pump on a glass surface, or something hollow, like an upside-down plastic container, on a metal shelf or on a stereo speaker naturally makes everything worse as those objects amplify sound and vibrate with the pump.
Relocate On Something Soft
Placing the pump on a soft object, such as a folded towel, or a thin chair cushion will absorb more of the sound and won't affect how the pump runs. An old rubber mouse pad is perfect for this as it not only absorbs sound but also prevents the pump from vibrating itself off the edge of whatever surface it's resting upon.
Replace the Diaphragm
When the rubber diaphragm, the part that vibrates inside the air pump and brings in the air, goes too soft or too brittle with age, it stops working correctly or breaks. This will result in little or no air being brought into the tank for the fish and makes the pump work harder, causing more noise. The diaphragm is replaceable and should be checked frequently.