This small almost silent air pump is great for nano tanks. It also is a decent choice for adding an air stone to an existing larger tank. It runs off USB, which means it's great in a power outage situation with a battery pack back up(purchased from a retailer like amazon*) used for cell phones. With the clip you can also hang this air pump from above your aquarium eliminating the need for a check valve. Also gives you the ability to hang it in a car for a long trip fish purchase. These are so versatile.
The air output is lower than standard air pumps which allows it to run near silently and uses very little electricity. This means it is best suited to run small sponge filters or an air stone. Great for shrimp and betta tanks, or making sure oxygen is in your larger aquariums.
Comes with the USB plug in adapter.
*link to amazon is an affiliate link.