sand from the lake at my cottage (throughly washed before placed in tank)
adds a really cool effect when theres enough current in a certain spot becuase part of the sand is quartz(which is white) and another is feldspar and mica (red) and the quartz isn't as heavy so when the current is strong enough if leaves ripples of red and white in the sand and looks very cool
EDIT: wow didnt realise this was in the stingray section.... from what i know about stingrays i would never use anything other than pool filter sand with them. With anything else though i'd use play sand that is throughly washed
I also would like to see the T grade. I still can't find any 3m up here but If I could I think I'd get T grade. I've used play sand and its OK but I'd love to try black.