....I lowered the front of the bed so that it looked better against the front glass. Critters are suppose to inhabit the top, aerobic zone but nothing gets passed the two screens into the anaerobic zone and the stagnant zones.
I wanted to see into the plenum so before I installed anything, I encased a plasticized magnet in epoxy and placed it on the bottom piece of glass in the tank. The stand that I had, allowed me to look up through the bottom of the tank. In about a month a layer of detritus formed on the bottom glass. In a few months, I put another magnet up to the first one and was able to slowly and carefully drag it around through the sediment. I could see that it was very uniform at about 1/4 inch thick. I only did this one or two more times over 8 years or so. It wasn't too exciting.
When I tore the tank down, I was very careful, like a paleontologist. When I got through the sand beds I looked at the bottom sediment and there was that same depth of 1/4 inch of detritus that formed in the first few months.
It appeared to me that something processed this stuff. The screens are there to keep out critters and there weren't any dead skeletons, shells or any other forms of remains. This led me to think that the last vestiges of detritus must have been falling to the bottom slowly and bacteria was (...well not eating it but) processing it away. The ATS must have been the eventual vehicle for export of detritus byproducts that come from different stages of decomposition.
In nature, on dry land, fecal excrement is not the last stage of nutrient breakdown. Otherwise, we would be buried in it. It is broken down whether it is in the soil or sitting on the sidewalk. There is always something that lives off of what that last organism left behind. To some degree, this can be done inside of a closed reef system, although removal is far better where possible!!! Never the less, there is a complex food chain going up the latter before food enters a fish's gut. Likewise, there is a complex and little understood chain of organisms that process that food after it leaves the gut. "Dust to dust" and all that?
...[ refering to a standard deep sand bed ]...In a Deep Sand Bed, I would think that whatever is deposited at the bottom is pretty close to inert. In any case, I think that the ticking "nutrient bomb" is much less of a potential problem than many people think. Yes, it is a sink but a very good one.
Again, this is keeping in mind that my ATS took up waist and heavy metal that might not otherwise get processed in another tank. I don't know.
As a side note, I have a thin sand bed in my current tank that is there for cosmetic reasons only ...[because I tried a diferent kind of sump with a different cryptic zone that also included a deep sand bed.].... I kept the sand bed in the sump but took out the cryptic zone.
I do not suggest that anyone use any of these methods.
