For a 1 to 2 inch sandbed, about 1 to 2 lbs per gallon in a standard 55. You don't need to get live sand -- you can buy dry sand and save yourself some money. As to the color, that's up to you. It's all personal preference. For large tanks, I prefer white sand just because it looks natural. But in my smaller tanks, I have used black sand and liked the way the corals' color stood out.