Close up view of a patented AAP Hydro Sponge Filter, showing the pores and higher bio and debris trapping capacity of these unique sponge filters. This particular sponge is quite full of organic debris based on this close up inspection, an amount that would stop effective flow with most of the common knock offs.
Sponge Filters, Canister Filters, Fluidized Sand Filters?? Not sure which to get for your tank project? This article gives a run down on the perfect filter to get. http://www.fishbeginner.info/home/what-aquarium-filters-should-i-choose/