If you’re in the market for a new air pump, consider the Silent Giant by Hydra Aquatics. It might just be the quietest aquarium pump on the market. You can see a video of it being tested against a couple of other comparable pumps, including Danner, on the Aquamanknox YouTube channel here.
If you’re new to shellies (typically short for shell dwelling cichlids), give serious consideration to the size tank you choose. Sure, shellies will work in both small and large tanks. However, if you don’t already have a tank, consider one that is lower profile.