Hikari Cichlid Gold and Bio-Gold+ worked wonders on my oscar. I got it when it was 2 inches and was a totally washed out brown until 5-6 inches when I started feeding it Cichlid Gold. It's around 9-10 inches now and has Deep Shiny Red scales. You'll notice a color difference after feeding it for a month. I've also Heard NLS and Omega One are good too, but haven't tried them yet.