Well, i think it is written by someone who has a very basic understanding of zeolites. While I don't know much about zeolites at all, I know enough to know that the article is pretty lean on even a moderate understanding of them.
There are industrial chemists which spend there lives studying categorising, and even creating zeolites, it is a simple name for a very broad group of minerals, all with very different properties.
The way he explains it, there is no need for the zeolite at all. All it is doing is acting as a surface for bacteria to grow, providing regions for an oxygen gradient where different bacteria can do their thing in reducing nitrate to nitrogen gas. The surface area available on most activated carbons it much greater than a similar volume of zeolite, and would make a much better media if this were the case.
His explanation really discounts the ion exchange process, and says that it effectively acts as a DSB.
I don't think this is necesarily the case. I don't know enough about zeolite, either natural, or synthetic to say for sure, but I think ion exchange is more important than the bacterial processes, for the simple reason that the pore size in most zeolites is far too small for bacteria (by a factor of 10) and the surface are colonisable by the bacteria is too low.
So I think when the right zeolites are used in marine tanks, their effect is more from the ion exchange rather than the bacterial action.
Layton