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as far as your filter question, i believe that the 304 is rated for up to approx 80 gallons, so you should be perfectly fine with it considering they always say it does way more than it really should.
of course this depends on what fish you plan on keeping. if you have a lot of fish (or a few very messy ones) you still may want to go with the 404.
good luck!! hopefully someone with more experience with one will chime in.