i have a jewel tank.not the same size but went through changing all the sponges . the only one i change now is the white one weekly but bought a big bag of filter floss instead.same thing but in large bag or box. much cheaper than jewel ones and does exact same job. dont use black sponge anymore either, only to remove meds . just added extra blue pad instead or nitrate sponge. i do a water change weekly , every couple of weeks i rinse 1 of the sponges in tank water and a different 1 next time.