Don't know if you've solved your problem already, but I have an Eheim 2224 running under my tank. I've had problems with the flow rate twice. The first time it was the impeller. Changed it.
The second time, I tried cleaning the impeller, taking some of the filter material out and all kinds of other tricks, but what ended up working was cleaning, or actually changing, the hoses. They were full of... well, gunk. So, try that, if nothing else works.
The second time, I tried cleaning the impeller, taking some of the filter material out and all kinds of other tricks, but what ended up working was cleaning, or actually changing, the hoses. They were full of... well, gunk. So, try that, if nothing else works.
