I suggested in the first reply to get a cup of LS
and spread it on top of the dead sand
Silica Sand can be used but the edges of the sand are sharp and it is not as critter friendly. Plus it won't give you the buffering that aragonite sand will.
If you want to use sand from the ocean, you could collect it and then bleach it to kill anything harmful. Then re-seed it afterwards. This is legal I assume to collect sand?
*180 gal Display, 100 gal basement sump, 33 gal refugium, 3x250 MH, 2x160 VHO actinics, zoos, some softies, LPS & lots of acros and other SPS.
*100 gal prop tank plumbed into main system w/ 2x96 PC lights and 1x150 MH,