I use the Fluval with my skimmer (saltwater). It works great!
Yeah after tinkering around with the Eheim one all day I ended up ordering the Fluval one. Apparently they fit the 12/16 hose of the 2215 and are meant to work a lot better.
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3ft 160ltr fresh/cold water, two small fancy goldfish, eheim classic 2215, a few (real) plants.