As some of you might know, I am trying out a relatively new substrate for Pings as a subsitute for sand of a suitable grain size (circa 0.5 - 1 mm in diameter). I am now using diatomite which is made up of fossilized diatoms (a kind of microscopic unicellular algae with silica cell walls). They retain water for a while but will dry out in a couple of days or so, depending on environmental conditions. This will ensure that the plant's roots do not dry out and also provide adequate aeration to the roots. In some pots, especially those outside the house, I add a pinch of peat to help retain water in case I forget to water the plants for one day.
eBeyonder, your pings that are with me are in diatomite and so far they look alright. Maybe your growing conditions need to be looked into. Too much water perhaps? I keep my Pings slightly on the dry side. I usually do not put them on a water tray, but this also means that you have to be very careful not to let the substrate dry out totally. With diatomite and some peat, I have at least one day's grace before the plant totally dries out and die.