Sand for a reef tank.
 

I have a large bag of crushed coral that I kept for years in the basement but somebody told me not to use it because the food gets in between there and rots causing all sorts of problems. What would be the best sand for my reef setup.

You should get fine sugar sand and stay away from crushed coral. I have samoan pink or something like that and it is great. Make sure you get aragonite sand instead of silica sand to aid in water buffering. Also look into oolitic sand, it is safer for your inverts and gobies, other sands might be too sharp and will damage fishs' delicate gills. Just my $0.02