mhmh
I think you missed it in my post above, they sell what you need as a replacement part for $5 or so. I dug the one I got out of a bin at the LFS. The link was just so you could see if that was what you want, I realize its not the same brand but it should fit. After all, the power filters fit on the same size uplift tubes so the prefilter has to be the same size. When I built my RUGF, I put that sponge on a different brand, Regent but not sure. I tryed putting a section of plain sponge over a HOB filter to keep fry out and it restricted too much, talk about low flow. The prefilter from marineland is more course than a regular sponge you buy from walmart in the cleaning section, it is like the sponge block you can put in the ac filters. I dont think you will be happy with a regular sponge (I wasnt) but it is cheap to try (I had some already at home). If the sponge tube is not what you want, might try the ac foam blocks to cut to what you want.
Hope I cleared my first post up a little.
Stias'