I made a homemade sponge filter. Just use a powerhead, an undergravel filter uplift tube, and some 3"x6"x2" filter media foam blocks. Cut a hole in one of the ends of the foam and carefully stick the undergravel filter uplift tube halfway inside it but do not make it poke out the other end! Then you can place the undergravel filter uplift tube with the foam pad onto the powerhead intake tube. With some further modifications this can be made to fit over a power filter uplift tube as well. This will add an additional source of biological filtration and reduce costs of replacing filter cartridges as often.
IMPORTANT: A key to this is to get the recommended size filter foam blocks that I stated above! Thickness is better than surface area!
You may be able to use a large household cleaning sponge but make sure it has not been used for anything, preferably buy it new and rinse it just to be safe.
DISCLAIMER: I have not tried using a household cleaning sponge so if you try this method do so at your own risk.
Below are example Images as to what to look for to assemble this:
(of course you can modify the parts shown here to fit your preference)
WARNING: Puffers are mischievous little blimps with enchanting powers. You may not be content with having just one.
