What size oscar?
That is not enough filtration, but if the oscar is still small enough it may last for a while. The best thing is a canister as mentioned. I use Fluvals.
They need lots of biological filtration, which the Biowheels should be all that is needed. But they also need a lot of mechanical filtration. For that the best thing is a canister because they literally force the water through, rather than in HOBS backs which allow it to flow around or over the media.