Regular sand is made of silica and mined in Utah and other parts of the Rockies. When you introduce this sand to salt water, it causes the water to get to lethal levels. LS is aragonite sand that is mined from the ocean bottom (about 10 to 20 miles off shore) and washed before bacteria is added and bagged up for shipment to fish stores. If you use sand off the beach, you run the risk of putting tar/rubber from near by roads along with oil from the ocean curl in your tank. If available, you can get carribean play sand from your local hardware store...if you are lucky enough for them to carry it. It will run you about $5 per 50lb bag. I believe a few manufacturers are Southdown, Yardright and Old Castle. If you can't find these, you can do a test yourself. Take some white vinegar with you to the hardware store. Pour the vinegar on the sand. If the sand bubbles, it is aragonite and you can use it in your tank. If it does not bubble, it is silica and is not tank safe. If you get lucky and find aragonite, make sure you wash it thoroughly with RO water and RO/salt mixed water to make sure you wash away all the impurities before pouring it in your tank. HTH