Poret foam largely used in sumps as mechanical and bio filtration. But I've also cut it up and use it as prefilters for HOB filters. Really good stuff. Highly recommended.
I posted another thread about how I let my poret foam sump go about a year before cleaning. Amazing stuff. I got it from swiss tropicals back when our dollar was betterAccording to the Fish2Water guys if look at their analysis Poret foam used in Matten type filters continues to build up bacteria load for several months. My application is in hard scape tanks like African tanks and grow out tanks with a heavier feeding regime.
Swiss Tropicals in the US has some great applications, videos and products. Most of their product line is sold in Canada by AngelFins where I have ordered my items from or DIYed it.