I bought a used aquarium the other day and it came with 2 white bags of substrate. Hand written on the bag is as-1. The peson I bought it from said it was crushed coral but it looks like sand to me. I did the vinegar test and it foamed so I am assuming it may be aragonite sand but want to make sure. Any ideas?
What you have is coral sand. It's the same thing as CC, but much finer. Actual CC is generally gravel sized chunks with shells mixed in with it. Sand is prefered over CC because it doesn't provide large cavaties for detritus to settle into and rot.