Depends on the tank and stock too. In my 180g with the tangs and lots of other fish my skimmer is full of a thick almost motor oil kinda consistency. It reeks to high heaven it glops out when I clean it. Totally gross lol
On my 90g and other tanks its a dark brown usually, liquid no doubt but a nasty black liquid.
You can adjust the type of skimmate you get by adjusting the skimmer. Just depends on the skimmer as to how to adjust it
180g Reef - 60g Rimless Reef -90G FOWLR- 125g Malawi Cichlids- 40b REEF- 34g Fresh Planted-working on- 20L FOWLR- working on
I have a mix of many different saltwater fish amongst my tanks, but I love my Tangs most of all.