I bought one on drsfostersmith before
It pulled out some brownish skimmate but not much
i sold it for like $10-$15
Now I bought an Odyssea PS-75 skimmer which is supposed to be very good for its price
It costs $30 on aquatraders.com
there is a great thread on reef central about it
its called Woot Odyssea needlewheel skimmer or something like that
you should check it out
the pics of its skimmate show it as being very dark brown to almost black