A method and apparatus for aerating a surface layer in a stratified liquid body using a depth-adjustable, fine bubble, surface layer aeration unit comprising: a body comprising at least one hollow internal structure; an air inlet communicating with the at least one hollow internal structure, whereby air from an external air source may be introduced into the at least one hollow internal structure; at least one fine bubble aerator communicating with the at least one hollow internal structure, whereby air from the at least one hollow internal structure may be released through the fine bubble aerator into an adjacent fluid; and at least one weight pod attached to the body, wherein the at least one weight pod comprises structure for adjusting the weight of the at least one weight pod, whereby the buoyancy of the aeration unit may be adjusted so as to permit the at least one fine bubble aerator to be positioned at a desired depth in a fluid body.