I went to leslies pool supply and got 4 bags of pool filter sand for $7 a bag. It sticks a little, but as it slowly gets a organic film on it it sticks less and less. Rays love it and no damage to them what so ever. The arguement for non-silica sand is humurous to me. Only other types commonly available are calcium based (will raise your pH and compacts easily, not to mention costs a fortune for a big tank) or maybe basalt (the black sands). Other than that most sands are made from the most common mineral around which is silica.
