Help W/MRC Skimmer

[wvreef]

Ok I have a MRC skimmer hooked up to my 180 reef tank....I am having trouble getting it to skim like I think it should...It skims but the stuff it is pulling out is a light green color and has never been a dark brown....I went by the manufacturer directions on how high the water needs to be but I still think there is something I am missing....

 

Now the set up it is set up externally being run by a pondmaster 18 1800gph it is going up and out of the sump thru the wall and into the skimmer then back out skimmer to sump by going up and over and down into the sum total head is around 4 ft. total both ways.... I only have one beckett air intake on the skimmer have water level when off to just under the bubble chamber....

 

So any help with this will be greatly appreciated....

 

Thanks All