hmm, thanks for the link homer, thats interesting. Now what would you say would be the problem relating to cories. Would it be that the sand grain is too small which leads to their dimise, so going with a more of a gravel instead of sand substrate would be better?
I think(just speculation) and have not really tested the idea is that the coarser/the rougher the sand the more likely it may be too erode the barbells of cories. There are a couple of things that could avoid this. If you have a sample of sand that you want to try, run your fingers through some, if it feels soft and silky, it should be okay. If it feels coarse and sharp between your fingers, I would not risk it. Also, if you know of a river or lake with some catfish, that has a natural sandy bottom, you can always grab some of that sand, be sure to fully sterilize it by boiling in water and use that. Chances are if it is not sharp enough to erode the barbells of catfish native to the river or lake, then it likely will not or should not erode the barbells of your your catfish.
I had a peppered cory catfish and dwarf aquatic frog in a small filtered 2 gallon tank. The tank was not planted and I was not into planted tanks. I did weekly 50% water change and gravel siphoning, the gravel was just plain epoxy coated gravel(I think 2-3 MM grain size). Believe it or not, the frog survived about 7 years and the catfish died after 9 years. To make a long story short, I only have experience with regular gravel and peppered cory catfish. Lol, I don't want to run cruel experiments on cory catfish just to satisfy my curiosity as to how sand would work
. That is why I have avoided purchasing catfish as tempted as I have been as the tanks that I thought of putting them in either have a sand bottom.