IMO....They suck....I have been using them for awhile now, and everysingle one I have had died on me...either the impeller broke of it just stopped working, or the aqua-lock system started to leak...THEY SUCK!!! I would go with a RENA FILSTAR XP3 or EHEIM PRO II....
i have an old 303 which is still going although it has been serviced regularly. they are known for wearing out impellers so keeping a spare would not go a miss.
dixon
When 404 just came out and I upgraded from 403, it was the best damn thing! The filter did its just and serves me well, if you are on a budget than go for it. XP3 and Eheim would be a better choice, like stated above.