I wouldn't buy anything 'fish related' at Wal Mart. Not even supplies, as that runs your LFS
out of business.
Anyhow, Wal Mart likely won't have the right kind of playsand in your region. Typically the only 'right' playsand is available in the northwestern area of the United States...everywhere else the playsand is the silica based junk.
I'd skip live sand and buy a 20lb bag of Carib Sea's Aragamax sand. Half the sand sold as 'live' isn't live anyways. However since you're in Florida, you might be able to get real live sand from a fish store, that wasn't pre-bag'd 6 months ago at some manufacturer's...but sand that the LFS
employee's actually collected themselves.