Dry sand will cloud your tank when you first fill the tank with water and it could tank a few days to clear up. So if you do use it cover it with garbage bags and fill the tank by pouring water into a bowl placed on the bags. Leave the bags in until the tank is full, this will cut down a lot on the cloudy water.
Clean up crew IMO
1 crab per gallon is way too many. I have maybe 40 in my reef and I also have about 30-40 snails. And IMO
they will not bread in a tank, if they do they become food.
in a bag IMO
is not worth the money... Buying play sand and then getting 5lb of real LS
to seed it would be the way to go..