white bubbles

[Salt Freak]

I'm getting white bubbles that are about 4mm big in the protien cup when i dump the bubbles there is also a brown water in there. I have three fish yellow tang, neon dottyback, scissortail, also have a cleaner shrimp. my tanks been up for about six weeks just put in skimmer on tuesday, the tank also cycled in 3 weeks.
what is it the bubbles. the skimmer is a berlin air lift 60

I'm in my third peroid class Business computer information system

 

[Great Lakes]

Are they being created in the collection cup, or raising up in the water coulumn?

 

[Salt Freak]

collection cup