well from this 35 year newbie “that didn’t just buy it and was fascinated by all aspects of the natural processes with the ocean”, oh and have been in it observing and collecting as much as possible for all those years, i always have some where a feasible wet section that is loosely based on the under gravel principle, the water has to pass for sometime through relatively fine calcium based media with in the aquariums water.
Of course with only 20 years experience your refiltering capacity would not sustain such a thing at full function after only 20 years experience.
The need to keep this type of thing clean is virtually never applied, so they fail, virtually always do!
If you did this it would most likely be full of rubbish with in 6 months to a year for sure and be failing nicely, they don’t work the way most use them, if they did use them that is and are left with a nitrate factory or hydrogen sulphide factory, either way it is a fail!
There are species of protists, you know the family name that was once protozoa, you know them surely, they comprise in part of white spot, velvet and so on.
Well that family has with in it; species that like to graze on and many use symbiotically some of the bacteria species that represent your nitrogen cycle bacteria.
I use them by providing where they can exist in supportive numbers and more to help keep the parasitic varieties as juveniles of one of the most represented forms of life in your aquarium, being protista, at bay.
You know when the aquarium is more or less mature, that’s these guys doing their bit, along with many other functions of course.
20 years hey, cool!