I have a Warner marine mf 201 skimmer. I have been trying to get this thing to work right and I cant figure out what to do. I called John Warner and he told me water level needs to be 9" and the air bleed valve unscrewed all the way. I redid my sump and followed instructions. I just cant get it to dry skim. The skim cup is light brown. Then I posted here (cr) and some people advised me that the water level should be 8" so I went ahead and raised my skimmer so it is at 8". Still it skims brown. What should I do? I have a 90 gal corner flo with a 30 gal sump.