Poret foam is a bio-media. It is also superior the the Eheim noodles or Substrat. I set up my 3rd Eheim Pro II recently and it contains 100% Poret. This was done on the advice of Dr. Tanner of Swiss Tropicals.
I have one more Eheim I will be setting up. It is the larger 3 basket model of the pro II. In the one above it is filled all 20 ppi, the 3 basket model will have 10 ppi in the first basket and thn 20 ppi in the other two.
I clean my canisters twice a year.
Here is a very relevant quote from Dr. Tanner:
What does that mean for aquarium biofiltration?
Water filtration is teamwork by the members of the substrate microbial community from all domains of life. This is an important conclusion, both for freshwater and marine habitats. The different players form a food web, where most organisms cannot exist alone but are interdependent. The microbial community varies greatly depending on the availability of foods, pore sizes, and substrates. Soil biofiltration is therefore very plastic, meaning it can cope with a variety of conditions. However, one feature is common. Natural layers of biofiltration are usually undisturbed for longer periods of time (many weeks and months). In nature, no one squeezes out the debris or rinses the media on a weekly schedule. Occasionally, seasonal floods or rains may “wash” a gravel bed but regular rinsing of the filter media is not happening. The microorganisms eat the debris and the sludge is completely broken down into gases and soluble products that then escape the pore space. Soil biofilters are almost maintenance-free. The released substances are either getting into the atmosphere or are taken up by plants.
For aquarium biofiltration to be most effective, filters should be running undisturbed for as long as possible. Filter media that remain passable and have a variety of pore sizes are best. Given that we like to influence the water parameters depending on the species we keep, and thus make water soft, hard, etc, the filter media should be chemically inert, so that it does not affect the water chemistry by itself.
When I first began using Hamburg Matten filters and the filtration in a tank was a single large Poret foam and nothing else I was worried about water clarity. That worry was quickly removed as the tank water is as clear or clearer as it was when I used more traditional filters with some floss in them. The best part of Mattens, and what drew me to them, is they only require cleaning once every year or two. I also find I only need to clean the Poret cubes (which replaced many of my sponge filters) about every 3 to 4 weeks.