I have a MRC beckett skimmer that seems to have really gone downhill, but I don't know why. It is driven by a pretty powerful pump, but it just doesn't seem to be generating the bubbles it used to, even when the air valve is wide open. The air intake seems to have a decent amount of suction, but I honestly don't remember what it is supposed to be.

I've cleaned to skimmer and I have cleaned the becket injector. I don't know of anything else to clean or check on.

Any suggestions?