Dont feel bad Nigel...I just got a Berlin XL and I am not too happy with it thus far.  Maybe we can trade notes and between the two of us, get them working as advertised.

Marks right, some chemicals or additives will affect the skimmers ability to produce.  As Ryan said, keeping it clean will keep production from slacking off.

Protien skimming, the use of activated carbon and an algae scrubber/refugium all do basically the same thing. They remove organic molecules from the water. But they are not an exact duplication.

Sometimes I would use carbon for just a few days if some kind of toxin was released into the water, through the death of a large coral for example. Ordinarily a skimmer is all that is necessary, though even that is questionable. Many of us go skimmerless and are doing just fine. Coral and other filter feeders like some crabs, feather dusters, small green chromis, etc. like to eat some of the stuff that a skimmer takes out of the water. I have an article about this. If you would like to read it, please email me separately.

Did you know that bristleworm larvae make up a large portion of the zooplankton in an aquarium and are food for filter feeders? Skimmers remove these planktonic organisms! Most recommend that skimmers not run 24/7.

Carbon will not remove planktonic organisms, but by using carbon you are taking away from what the skimmer could be doing and you are needlessly spending money on carbon.

My opinion is that a tank newer than yours and a much older tank than yours are not in as much need of a skimmer, unless the aquarium has lots of surf zone stony coral such as acropora.

FYI - my understanding of Elegance coral, a large polyp stony, is that it comes from areas near sandy seagrass beds where nutrient levels are higher than the surf zone where acropora grow. So even though these are both stony coral, they have different nutrient requirements. Does anyone have a comment here? Does anyone feed their Elegance?

Nigel, did you get an Emporer Angel? What size and in what size of tank? And what province are you in? I'm just curious. It's neat to have someone in the group living so far from Utah.

Mark's 2 cents

It can go long periods of time without production and then all of a sudden one day...

Some chemicals can affect it. Feeding or simply placing your hand in the tank can interrupt the foaming action, because of oils.

What is the age of your set-up?