"Cryptic, Macro, or both?"
I would only caution that you don't go too low on nitrates and get nitrate limited.
...the Redfield ratio...which tells us that the elemental composition of marine organic matter is composed of carbon, nitrogen, and phosphorus in a roughly 106:16:1 ratio.
This could inhibit algae growth including macro or even calcareous algae. This may be unlikely but it does happen. If your nitrates are very low but your phosphates stubbornly begin to slowly rise, it might be the culprit.
Some people that dose vodka run into this problem from time to time. I have a true ATS and when I experimented with vodka, my calcareous stopped growing right away.
My dump bucket style ATS is custom designed and built by me. I started using standard window screen and when it wore out I found that I no longer needed to use a screen because it was growing right on the clear plastic.
The purpose of the design (that was inspired by the inventor Dr. Adey) is to get as close to the maximum growth as possible by breaking the surface tension around each individual strand of algae and getting more water contact, which improves respiration, nutrient uptake and light absorption. Part of the point is to have zero clumping.
This is done by first, allowing the algae strands to get flooded and then get a strong rush of laminar water flow as the water passes out of the tray. The next phase is a quick reversal of the remaining water flow that culminates with water crashing into the back wall of the scrubber. The crash causes lots of turbulence.
What I am saying here is that very little detritus is trapped in this type of ATS yet it works quite well. Going back to my new tank, before my bacteria got going, I got orders of magnitude more detritus ON the sand bed than got trapped IN the algae bed. Nutrients are indeed taken up after rotting and that is the way that I like it but the rotting does not actually take place inside a well designed scrubber.
Now, when I read about the cryptic zone I tried what is described below. You probably would not have the results that I had because you are skimming. Vodka, an ATS, a DBS and a cryptic zone at the same time was over kill so these results are outliers.
I mention these only for reference. You can dismiss them because they are not scientific experiments. I have a very different end game than most because I am trying to grow NPS corals so I feed very heavily but need my nutrient load very low as well.
My old tank ran well for 8+ years before I relocated and now I am running a lot of experiments so I get some odd results but I learn from them.
This is only a very subjective observation of my case study number one. I put a DSB of 8" in a 55 gallon sump tank that was connected to a display tank of 130 gallons. The rest of the sump was filled to the brim with a very porous coral rubble. I put only 2 gallons of DT water trough the sump per day. within a few weeks, after harvesting algae, it didn't grow back. I upgraded the lighting and played with different lighting schedules but it never restarted.
I went for years without any active filtration. A had no mechanical what so ever. I just had aeration. My nutrient parameters stayed stable but the phosphates slowly began to rise over time. Now I am starting to dose nitrates to see if things start to turn around.
Case study number two(a prequel) In my old tank, I had a Jaubert sand bed. For those that are not familiar with the popularized version that I am talking about, I will describe it.
I had a plenum or open water space of about an inch on the bottom of the tank. A layer of screen with 3 inches of coral gravel was on top of that. Another screen was on top of the gravel, with 4 more inches of coral sand on top of that. I lowered the front 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 an 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?
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 an ATS takes up waist and heavy metal that might not otherwise get processed in another tank. As a side note, I have a thin sand bed in my current tank that is there for cosmetic reasons only. 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.
the shallower the substrate the less food available for any living population of organism. the more food the more organisms. 
