Eheim has better bio effeciency, it has been proven in a lab test compared to the fx5's, what they found was that the fx5's were a little bit better at removing suspended particles from the water due to the large number of foam blocks. And depending on what your keeping in the tank I would prefer bio filtration over mechanical as most filters these day come with more than enough mechanical filtration and not enough bio filtration, I guess it all comes to down the the fish and how much waste their making.
Also the fx5 hasn't got anywhere near the flow rate that it claims to have as they test the flow of the motor by itself, not the whole system with media etc.
There was a link here somewhere where the thread was posted on monster fish keepers.com.
But in relation to the subject, did the fx5 have instructions as to how the media should be arranged inside the filter?
I've always thought its better to have the water travel throught course media 1st and then bio media through to fine spodge (I don't like using wool)
