An apparatus and method for controlled ventilation and aeration of liquid medium includes a dome supported by a flotation device, a lower housing supported by the flotation device, the lower housing connected to the dome, wherein a sealed space is defined under the dome and above the flotation liquid, one or more orifices, the orifices configured in the dome, and an aeration apparatus positioned within the sealed space and partially submerged in the flotation liquid, wherein the aeration apparatus comprises one or more parallel shafts, at least one first disc positioned axially on one of the shafts, at least one second disc positioned axially on another of the shafts, wherein the second disc is interleaved relative to the first disc, and wherein a surface of the first disc rotates in a direction opposite a surface of the second disc relative to each other resulting in a mixing area therebetween.