i have one in a breeding tank-its definatley not my favorite filter. i thikn you are supposed to chang eit once a month but i do it every 2 motnhs. i am hesitant to throw the cartridge away because it has all of the colonized bacteria on it. if you get that filter though you need a valve on the airline as it is too powerful for the betta to be comfortable.
i would go with a sponge filter or a corner filter that you can put your own media in. then you wont be throwing away all of the good stuff whne you change the carbon.
