long as the black sand is "aragonite" you can use it no problem.
Live sand speeds up the cycle process. That is it's benefit when starting a salt tank.
so if your in no hurry you can save money and use dead aragonite. throw a few raw shrimp from the grocery store in and let it cycle for a few weeks with the rock. during that time the dead sand will turn into live sand
remember, salt tanks take longer to cycle than fresh so just be patient. i tend to be impatient and it has cost me money here and there that was not needed![]()