I have both on my 225 gallon. They both work great, but you can actually feel the vibration from the FX5's motor on the ground. Also, the baskets fit loose, and overall fit/finish isn't as good. Its good for the money though. That said, I'll never buy another one since the Eheim has a better feeling of quality from its smooth, quiet motor and nicely finished plastic - I like details like that. I honestly can't say that it works any better than the FX5, its just that it seems to do it more gracefully....the only analogy I can draw here is like the difference between German and American cars. If money matters to you, get the FX5, if it doesn't, get the Eheim.