I have the Fluval 406 filter currently and I couldnt be happier. The 406 is improved over the 405 as they added a better motor and better protection for the impeller. I have had it a month and the water is amazingly clear. I also have a 55 gallon. I would like to ask about your setup though. What else do you have in your 55 gallon. What kind of substrate are you using and how many turtles / fish do you have, any plants?
My setup:
viewtopic.php?f=3&t=33195I ran it for a month on the standard configuration that is recommened by the manufacturer and that was before I found the info on here about the recommended media setup. Now I have it set up with the right setup. (carbon and Biomax)
Feel free to PM me if you have any other questions or post on here. I am sure others may have the same question.