I HAVE A 75 GAL. FRESH WATER TANK AND CURRENTLY USING FLUVAL 304 CANISTER FILTER. I'M CONSIDERING GOING WITH A CANISTER FILTER WITH UV STERILIZER BUILT IN, ANY RECOMMENDATIONS ON WHICH IS THE BEST?
Is that the only filter on your 75 gal? If so it's underfiltered and your problems may stem not from not having a UV, but rather from not having enough filtration.
On my 55 gal I have a 304 and love it, but I also have a Marineland H.O.T. Magnum, which is rated for a 50 gal tank in itself.