A lot of ceramics (40gal), filter pads, and sponge.... These are only flter media i use in my 60 gal sump...
Always love the product, and always bring the good result.... If i can add in more,... I would~!!
There is always a debate between the result and efficiency of ceramic and bio-ball.... but what do i care, if i have more roomm i would even add bio-balls in my sump...
People use ceramics in their filter system to keep red arowana, leos, etc.... I dont think it will harm my cheap fish ....