I've been running two FX5s on my 225, and they're alright. Media capacity and the ability to customize it is good. They're kind of a pain to prime when putting them back on-line after servicing. I don't know if it's any easier on the FX6. All in all, not bad filters, but honestly, if I had it to do over with what I know, I'd go with something else. The biggest reason is that I've had to replace the motor on each once since I got them, around 2012 I think (I'm winging it based on my memory and I'm not 100% sure about that), and I think the motor is going out on one of them again. I expected more from a $300.00+ filter from a name like Hagen, especially when the replacement motor costs more than entire cannister filters of other brands. I know the FX6 uses the same motor unit, so I wouldn't buy one for that reason alone.
WYite