I just finished upgrading my 406 to an FX6 on a 55 gallon tank.
I try to clean the filter once a month. Sometimes it's longer. I'm pretty religious about weekly water changes. For some time now, when I do a water change, the 406 has not wanted to start when plugged back in. I've found that emptying the water, often without even then opening the filter, will magically make it work.
Monday night, Chicago and surrounding areas had two storms move through. I lost power with the first one. Only got power back today just before 2pm Thursday. I have a generator because power loss is not uncommon for me--though three day outages are.
The generator power isn't as clean as utility, and I'm constantly stopping it to add gas or move it over to the neighbor who doesn't have a generator so they can get their fridge temp back down.
Even Monday night I had difficulty getting the 406 going. By Tuesday night it wouldn't start. It might have been fixable, but I'm planning an upgrade to 125+ gallons within the next year, so I decided to take the plunge and ordered an FX6 off of Amazon on Tuesday. It actually arrived Wednesday, but I wasn't about to plug it in until I was on utility power.
Despite over two days without the 406, my water parameters are fine. I've also got the 55 gallon refugium that has four or five times the biomedia that the 406 had plus duckweed, which helps on the nitrates.
So a few comments comparing the two:
The FX6 is a beast. The water volume is huge and the coarse sponge pre-filtration is at least three times larger than the 406. The flow rates are higher, and with the two nozzles directing water into more of the tank, I can already see that I'll be siphoning up much more gunk.
I was surprised at the biomedia capacity comparison though. I had my 406 set up like in the filter topic here. The FX6 comes with enough biomedia to fill half a basket. I added all the biomedia from the 406, and I had some left over. Not quite as much as Hagen supplies, but pretty close.
So, the FX6 has a larger flow rate, a larger volume, a much larger coarse sponge capacity, but about the same biomedia capacity as the 406. I was surprised.
Oh, and the FX6 is quieter than my 406 was!
Wishing perhaps I waited for the FX6.
