When I tried play sand, this is what happened to my pump impeller.
the shaft is supposed to be equal diameter throughout.
Because I have medium sized cichlids, their normally activity would stir it up, and it would get sucked up into filters, and eat away at pumps.
To me it is not worth the trouble.
PFS is much heavier, enough so, that normal fish activity does not allow it to be sucked up. Well worth the extra dollar or 2 for a 50lb bag.