I have cories on playsand, also have loaches (for the moment) on sand. I use to have gravel.
I personally think that any bottom dweller appreciates sand much more than any other substrate.
Although there is a lot of options for sand substrates, I personally wouldnt use pool filter sand. I have, as mentioned, play sand in one, and overpriced "aquarium" sand in the other. (I like the end result better with the overpriced stuff, but the playsand is easier to deal with when cleaning and setting up the tank, IMO.)