http://www.jehmco.com/PRODUCTS_/FILTRATION/Hydro-Sponge_Filters/hydro-sponge _filters.html Here is link to the page. The filters you want are the ' H-0 ' they will fit shoe boxes and last forever almost. They have a lot of foam, so can handle quite the bio load. Lorraine To join the AKA see http://www.aka.org/pages/join.html Archives are at http://fins.actwin.com/killietalk/