A self-uprighting aeration device that minimizes turbulence and disruption of any sediment layer in a tank. The device includes a float positioned about a first position on a longitudinal axis of the aeration device, a ballast positioned about a second position on the longitudinal axis, and a diffuser. The float and the ballast are configured to orient the aeration device in a liquid with the longitudinal axis substantially aligned with a gravitational vector to dispose the diffuser above the sediment layer. The aeration device can be configured to rest on a support surface in the tank or float above such a support surface. Methods for aerating liquid in tanks with the aeration device are also provided.