Alexander and others
I want to clarify one thing hear that is misleading to a degree. It has been brought up before.
The zeolite with its porous surface is among other applications used to host bacteria in a huge quantity.
There is pore structure and then there is non- pore structure. The pore structure of zeolites is based on it pores size. There are no bacteria that can grow within the pore structure of any zeolite as the pores are way to small for them to fit into. Even nano-bacteria can't fit. All one has to do is look at the Angstrom size of the zeolite pores and the Angstrom size of the bacteria.
So what is non- pore structure ? When zeolites grow they may not always grow as a solid mass. They may have what we can call "pits", "vugs" min-caves" or open channels and these are not pores or part of the pore structure as defined in the nomenclature of zeolites or any molecular sieve or ion exchange media to include things like GAC.
With that said these "openings", as listed, can house bacteria. One thing that is known about zeolites, is for what ever reason, they like to colonize it more so than most other media for some reason or reasons which may or may not be debatable. However, this can be said of almost any substance. If you ran some growth rate test on different media, to include even smooth plastics of different composition, you will see different growth rates. Bacteria have an affinity for the certain surface types, whether it is hydrophobic, hydrophilic or is polar or nonpolar. So the question has been asked and can be asked is there some other media that may work better ? I'm sure there is but there is no reason to try and debate it or even really look, as the zeolites work great. So, old saying, " if it is not broke why try to fix it "
Something else to look at that may make the zeolites such a good choice. I will call it "bacterial-zeolite interface diffusion rates". It may be that within the intrastrutre of the zeolite and is actual pore structure, that such bacteria, as facultative anaerobic denitrifiers, can release unwanted by-products into the pores of the zeolite. There even may be some small ionic exchange taking place.
Years ago we introduced something into this hobby called X-Nitrate, now with names such as Nitrate Sponges. These are all zeolites of the Heulandite Zeolite Series as the end-mineral Clinoptilolite. The same stuff sold as Ammonia remover for FW and at times in the olden days as kitty litter, and floor dry. These are capable of turning into a facultative anaerobic denitrifiers. Does this mean use this stuff instead of the ZEOvit zeolites or is it Ok to use them as a replacement. I would not, as even all Clinoptilolite is not the same from mine x to mine z. Choosing the right Zeo to perform z, z or z is not an easy task, unless you know what you are going. Zeolite chemistry is not an easy subject when you start to choose the right one for ionic exchange, adsorption or as a molecular sieve.
There are actually books written on this subject, just on zeolites and I have 4 of them