I am using the Berlin skimmer pump that came with it.
If you remind me how to upload pictures I can post a picture of it, but in the meantime I have attached a link to the Berlin website. The unit that that I have is the Berlin HO.
It is the type with a venturi (tube fed air). I have been trying that but seems to do this intermittently. Now had replaced the original air line with standard tubing. Could that be a problem?