Terrible advice you are getting here Mil26 in my opinion. Please do not waste money on this bad advice and replace your current sand. I say that you take about 90% of your old sand and rinse it very thoroughly until it runs mostly clear. You will have to rinse live sand, or dry sand the same amount regardless so why buy new? Live sand is a complete waste of money as you have to rinse any "live" organisms away so as not to have a cycle, and again horrible advice. Unless you happen to not like the type of sand your currently have, it would be unwise to buy new to replace what you have. I have had great success in transferring aquariums by having 75% new freshly made saltwater ready to go into your tank and 25% old, and put the cleaned sand in along with 5-10% dirty sand from old tank setup which will give you all the live bacteria you will need. If you know someone with a longer established tank, you can also ask for some of their dirty sand to give you more beneficial bacteria colonies. For the additional sand you will need, I recommend CaribSea Seafloor Special Grade Reef Sand as it is the best I have found and currently use.