So far my Aquatop CF400-UV has been great on my 75g. I am also running a diy 20g sump/wet-dry system fed by an overflow. The aquatop was cheap, about $110 at my lfs. I think the 500 series is about $30 more. They are dead silent, and can be filled with all types of filtration media. The only thing i didnt find so great was the stock plumbing pieces it came with, but I've come to feel they aren't that bad. So far so good, no problems with it, it does its job just as well as cannisters 2 to 3X it's price I think.
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