Any kind of filter sponge that you can fit over the intake tube. I bought some 'Aquaclear' foam inserts and cut them into small blocks. I then made a slit in each one in the middle and pushed on to the end of the filter intake.
It does need to be a reasonably coarse sponge size though to let the water through, otherwise it will get blocked with gunk too quickly and you'll be forever taking it off and cleaning it.
It does need to be a reasonably coarse sponge size though to let the water through, otherwise it will get blocked with gunk too quickly and you'll be forever taking it off and cleaning it.
