My Skimmer won't foam up

[kwirky]

have you removed the venturi from the pump and had a visual check of the venturi nozzle? I've had to clear rock hard blockages with a meat skewer before. Sometimes it's a little too hard for hot water to clear out.

your pump might need an entire cleaning with a vinegar solution. pick up a 4L of vinegar from superstore or something, and remove your pump, venturi, and impeller, and let them all soak in a vinegar solution of 2 parts vinegar to 1 part water. If you're nervous pulling your impeller out, it's usually fine to just drop the entire pump into the vinegar solution (just have to leave it in longer). I was having the same problem, and when I called euroreef, the guy suggested that once every 2 months or so. fixes most of my problems every time I do it.

oh, and if there's a valve on the end of the airline tubing, maybe try removing that? could be restricting air flow