im using weipro 2012 too but on AT-104 (2000l/hr) on my 2-feet (57L) tank.
tuned the water level to 0.25~0.5 inch below the collection cup. skimate is dark brown watery type and get thick dark brown mud round the collection cup opening after 3 days of operation after cleaned the cup.
if u want to get watery skimate which means more nutrients is removed (IMO better). tune the water level higher like mine or less than 0.5 inch.
green skimate? i dunno much on that. but i heard if a coral is coloured, the skimate is normally having the coloue of the coloured corals. so do u have a green colour coral in ur tank?
if so, the coral might be the problem.
or do u have lightings very near ur skimmer? if so, it might be algae growing on it too.
cheers bro, i will try to help u as much as i can.
regards,
LaW