I think you may have a different problem but as you know from my many rants I am in 'constant disagreement' with the many "You can't use a fine substrate as it will become anaerobic" statements as per my posts on TFF.
I have used plsy/silver/dry sand for a long time and a part from the small amount of cyno that grows along the front (as it also did with pea gravel) I have no problems. Large bubbles occasionally come from the substrate but there is no smell. This is on top of the Tropica substrate which has visible amounts of organic matter within it.
I'm also a very lazy water changer to the point that sometimes I can't be bothered for a few weeks in which time no detritus gets removed and still no probs.
The front of my 'scapes' is always plain sand. I do have MTS but they only burrow through the top of the sand and at the front it is 2" deep on top of the Tropica. At the back it is 3-4 ".
AC