should do weekly water changes and clean it atleast once every three months. keep a close eye on the parameters and if the toxin levels rise above 0 then do a larger water change or increase the frequency of water changes.
also depends on how the tank is sticked and with what.
it should say in the instructions of the filter media how often your supposed to replace it and cleant the impeller.its once a week for the carbon and once every three weeks to a month for the sponge i think. Some people just squigy it under the tap this looses the bacteria and stuff that help to cycle the tank. depends what your trying to keep in the tank but im shure allot of people here will tell you not to do this. i can allmost hear them from here shout louder guys.
Taking the filter apart and cleaning the tubes, impeller, etc, that's a true pain in the ^$%. I do that maybe every three months. Guess I should do it more.
Well in my Fluval 304 there isn't much to clean, inside theres just a bunch of trays that fit in together that u put in the amonia and the carbon into.
Every week, man thats alot for changing the carbon!
With a filter like the 304 you really dont need carbon. I currently have 5 tanks running and there isnt a carbon bag in the first. In your compartments you want to get some good gravel for baterial growth and then put a good filter floss in another and you should be good to go.
Fluval is one of the better ones on the market and you should be very pleased with how it performs for you