I have similar problems with my Euro Reef. I used to have to pour hot water into the airline tubing once every two weeks or so. My frustration is that once the airline tubing blocks up then the skimmer starts to overflow. Now, even after taking the pump apart and chipping away some salt crip with a knife, I have to use hot water every three days. Only on one pump though. I haven't done a good vinegar cleaning in a few months so maybe I'll try that.

One thing I found after many months of struggling to get my protein skimmer to work properly is how important it is to have a constant water level in the sump around the skimmer. My old sump did not have baffles in it so I would often (mistakingly) let the water level drop a fair bit before topping off the sump. I have since installed a sump that has baffles in it to allow the water level around the skimmer to remain constant and my skimmers performance has improved very dramatically. Now I just need to install an auto top off. I know a lot of people have baffles in their sump to keep the water level constant around the protein skimmer but I thought I would offer this suggestion for those that don't and are having problems with their protein skimmer.

If the hot water trick only lasted for a day there is still probably salt creep in the venturi intake. if the skimmer you have has a small venturi air intake you may have to clean it by taking it apart . I have a css 65 and have to clear the creep manually unless i catch it when it's just starting to build up