Not to long ago I broke down my bio cube and figured well why throw away the sand. So I cleaned the sand up and decided to make some frag discs. I wanted a clean look to them so i went with just 2 parts fine sand and 1 part white portland cement. I found some silicone ice cube trays for $5 a pair and used different size Dixi cups as molds. After pouring in the mixture I added sand on top of the disc and let them set. Since I didn't need them I let them dry out and cured them for about three to 4 weeks. The ph was about 8 after 2 weeks but I was not in a rush so I let them sit. Anyway just wanted to share how they came out. Not bad for reusing something I was going to throw out and I guess I will not have to buy any for a long while.