Ok for the carbon do I need to get a media bag to cover the whole sump returen or will just a smaller one in the sump work? (6"x4"?)

Carbon filtration will work fine as a passive process. If you want the most performance out of your carbon, consider a PhosBan reactor to fluidize it. Aside from that, just toss a small bag (high quality carbons only need like half a cup/100 gal) of it into the sump in an area that gets decent flow. Just make sure you knead the bag daily to keep the carbon from channeling.

Also, make sure you replace the carbon every two weeks or so.

cool thanks for your help.