Tetra Whisper Air Pump 10 to 30 Gallons, for Aquariums, Quiet, Powerful Airflow

Don't know why anyone gives these a low review. They are quiet and reliable and inexpensive. No pump lasts forever, but they outlast the fancy overpriced ones and are quieter than the "quiet" expensive brands. For super silence, I hang mine by the cord inside a big pickle jar with a hole cut in the lid. for the power cord and airtube. Then stuff the jar with a hand towel. Put the jar on something soft, like a rubber mat or folded up wash cloth. You'll hear the bubbles in your tank, but no way to hear the pump. Also, keep your pump higher than your tank for flood safety in case of disaster like pump failed, power outage, hose pops off, etc...