An aeration device adapted for the introduction of gas into a liquid medium is provided, including an elongated primary distribution member with a proximal end adapted to be connected to a gas source and a distal end adapted to be immersed into the medium. Additionally, at least one aeration member is connected to the primary distribution member at a location on the distribution member spaced from the proximal end thereof and being in fluid communication with the distribution member, adapted for bringing the gas into a state entrappable within the liquid medium. Also, a flotation member is provided, mounted onto the primary distribution member and adapted to assume various positions along the distribution member according to the level of the liquid medium. An aeration system is also provided, the system including an array of aeration devices as described above.