If you have not changed out your air stone or ornaments, it may be clogged now, and need either changing or cleaning. An old air stone will restrict air flow which will make a pump noisy. Also, check the air line tubing where it connects to the pump. If it is discolored, as in dark brown or black, pull it off, then snip the discolored portion off as it will be stiff and restrictive there too.
If this does not correct the issue, then open the pump and inspect the inside. Make sure the magnet near the motor is not actually hitting it.
Date published: 2018-07-18