I have thought about that too. but compairing the bubbles to the RO skimmer in the other tank. they just seem off small tinny bubble that dont produce a good foam head.Maybe your skimmer isn't pulling much because there isn't much to pull. Is there anything aside from LPS in the tank, and if not, do you add coral food? As I am sure you already know, a skimmer does nothing for nitrates and phosphates that are already in the water. The point of a skimmer is to pull detritus before it decays into N&P.