[sleeman]

I agree, the vinegar test is not perfect, but it gets you pointed in the right direction. I would assume that if the product is 100% Calcium Carbonate, that all it would leach into the tank would be Calcium. Now, Is this a natural product? How fast does it break down? what kind of buffering does it offer? And how much if any additional calcium does it put into the system? I don't have any of the answers, just a pocket full of gravel that if I add red dye and vinegar to I can have a science project for one of my kids. All I am trying to do is find a cheaper alternative to substrate and rock so I can spend more money on lights, pumps, etc.
Cheers,

Al