No rust specs before adding to the tank. I still have 75 lbs unused in the garage that I just took a look though (bought extra in case I NEED a bigger tank over the winter).
The play sand definately has a few impurities since there are a few black specs as well ( I would try a picture but since the sand is glowing white I don't think it will work) I think this was rust since it discolored the glass a bit where it was touching ( i was able to rub it out though) On my FW
tank I have a couple of rust spots from the gravel that was in there.
Right now I can't find any rust so there aren't that many bits ( I hid the bits I saw this morning cause they scared me too much)