I really like how some say skim is supposed to look like such and such, or else its not working right. Some say it should look dark black brown like coffee...... etc etc. What it all boils down to is what is in your tank, the size of the tankas sized to the skimmer in use, the bio load, the food yu feed, how you feed, and a whole host of other odds and ends. If its getting colored junk collected in the cup, its skimming......Is it skimming as efficieint as it should be.,,.,.,.hard to say, it may or maybe not, as it may be diue to skimmer design and thats all your gonna get. Lots of corals and rock usually makes a lot more darker skim, as compared to a tank with few corals and mainly fish....Some say you should be getting a cup of skim a day. Its bull hockey. Maybe my tank doe snot porduce a cup of skim a day, and maybe it takes a week........since no two tanks are identical. If your water parameters are fine, no odor etc, clarity is good not yellow looking let it alone and be done with it. I personally try and run my skimmers as dry as I can, so I get a darker skim and it takes longer to accumulate than a watery skim setting.........its all personal preference, but sinc eyu have a seaclown, just be glad its skimming as anything skimmed is better than nothing being skimmed.