have you pulled it apart to clean it? Sounds like something is clogging the water intake portion of the pump. Since you have lots of air bubbles I'm thinking the air intake to the pump is not clogged. Regardless, a good reef moto is when in doubt, take it out. (That's what she said.)
Seriously, most issues warrant a removal and full clean anyways. Give it a shot. I know chemiclean usually affects the performance of a skimmer and I'm sure you'll see its continued effects for a while yet. I just think if something is caught in the pump and you let it go without checking it out that it could cause harm to your equipment.
