use pool filter sand. You can get it at home depot for under 10 bucks for a 40lb bag. The grains are heavy enough so when stirred in your tank, it will settle right to to bottom and wont get sucked into your intake filter tube. Just make sure you rinse it good.
i just put play sand in my 95 gallon...got it from lows and it had a lil bit of clay in it but after about 5 to ten min of rinsing per bucket it was fine. it will take prolly hour to hour of half of rinsing. but i like the look and once in the tank if rinsed well it settles very quickly. i am satisfied and its like 3.50 per bag at lowes or home depot