We have recently favourably reviewed the UltraReef UKS 180 skimmer (review) and for the occasion we were able to measure the loss of
efficiency caused by poor maintenance.
Article available also in: italian
Let’s be clear, most people don’t practice regular maintenance on their skimmers. They simply clean the glass, which is the bare minimum, and little else. At best they clean the injector. But cleaning the pump is one of those incredibly important issues.
As I was saying at the opening, when we took the skimmer’s measurements we noticed that the measured values were not the ones claimed by the company. That’s why we took some time to figure out what had happened. But the first thing that came to our mind was to deep-clean the pump, both injector and impeller.
The injector can in fact get clogged up by calcium and salt deposits, decreasing the inlet air. To keep it clean you just have to let the air tube drink a glass of osmosis water once a month. You can find the complete procedure in this article.
The second point concerns the foaming pump. During the functioning it may happen that a small snail, a calcium deposit, or a pebble ends up on the impeller, and the apparently insignificant issue can bring the foamer to have a drastic inlet air drop.
But I did tell you I would quantify the differences. Here they are. The maintenance-free foamer had an air inlet reduced to roughly 430+10%=~470 l/h
Once conducted the cleaning, we went back to measuring 730+10%=~803 l/h
Non conducting maintenance brought to a inlet air drop of 41%!!! A more than significant difference.
Conclusions
Clean your pump and your foamer’s injector often. The injector once a month, and the pump once every six months. Keep in mind that if you clean it once every three months, your foamer will only be kept in better efficiency.
Or you can acquire an inlet air measurer, like the Sander we are using, so that you can understand when the pump has to be cleaned.
Impeller 
Injector
