Sand

[pix4c]

Is this OK to use an a reef tank? I usually use Fiji pink, which is a lot finer.

 

[EnterName]

Aragonite is mostly calcium carbonate (CaCO₃) which is perfect for a reef tank. There is some ongoing theory that the more coarse aragonite might be prone to dinoflagellate growth. But Carib Sea substrate is very commonly used in the hobby :)

People like using more coarse substrate as it doesn't get blown away by the current as easily, but it might be more prone to detritus accumulation, and would need to be deeper to allow for anaerobic conditions.