I too have the prizm skimmer, I too had noting but problem with it, until the handyman in me decided to make some modifications to it. I took the air hose that goes from the "plug" on the collection cup and put a inline air valve on it and left it hanging off the side of the tank. Then I took a 6 inch long piece of air hose and put it back onto the plug on the collection cup, just incase the cup fillus up too fast the water can return to the tank through that hose and stay off of my floor.
I think this works becasue there is too much air being mixed with the water on the prizm. That's what makes it hard to adjust, you can't tweak the water flow or the air being added without affecting the other. First I adjust the flow so that the water sit's just below the level of the o-ring on the bottm of the collection cup with 0 air being added. Once this level is stable for 5 or 10 minutes I slowly start ot open the air valve until there is slow and steady stream of white bubbles, skim, coming out of the top into the cup.
I've never been able to get the dark skim that others talk about, but I'm not sure if it's possible with this skimmer or not. I empty my collection cup about once a week and there's probably a 1 or 2 cups of light colored skim. Hope this helps
Eheim 2215 Canister
Prizm Skimmer (it works)
2 (1m/1f) Percula Clowns