Ghost shrimp? I'd be more worry about the kuhli. Kuhlis are really mellow fish; ghost shrimp have been known to get a little aggressive. If its dwarf shrimp you're worrying about, i still wouldnt worry all that much. But their babies might be fair game for the kuhlis if they fit in their mouths on it.
I have about a dozen to twenty kuhlis in my sand tank and i have observed then eating everything from frozen daphnia to beefheart. And if they could munch on daphnia, im sure that baby shrimp is about the same size.
With regards to substrate, im sure you could keep them in anything from gravel to sand. There are even accounts on loach.com about someone accidentally breeding them in a tank with gravel substrate. Personally, I use sand because they really like to sift through the sand for food. Its really cool seeing how they sift through sand and spit it back out through their gills. If you ever seen cory on sand, you might know what im talking about. This is the reason why i went with sand. You're free to use anything as long as its not sharp, jagged or in anyway going to scratch them.
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