Been installed for 2 months on a Red Sea Max 130 34 gal. water level sits about half inch below water mark on the tunze. Has anybody got any DARK SKIM from this thing? Im only getting a light green color water in the cup. Cup fills about half way every day, it seems to be filling just water tho, no real skim or gunk. The neck gets some gunk, needs to be cleaned about every 2 weeks or so. Anyone?