An apparatus for sterilizing or disinfecting fluids, which comprises a fluid conduit, an ultraviolet light source, which is at least partially within the fluid conduit, and an air drive unit coupled to the fluid conduit. The ultraviolet light source generates an ultraviolet light, which kills microorganisms in the fluid, thus sterilizing or disinfecting the fluid. The air dive unit creates air bubbles in the fluid, such as for fish tanks, fish hatchery ponds, or the like. In accordance with one embodiment of the present invention, the ultraviolet light source comprises an ultraviolet light bulb being surrounded by a protective sleeve. The protective sleeve preferably comprises a UV transmissive material, which may comprise a fluoropolymer material, such as PTFE, FEP, PFA, AF and Tefzel ETFE.