used rock

Hi everyone, I recently purchased some used rock that was left to completely dry out. Some of the pieces beak easily and are completely red with white patches. I was wondering what kind of rock this is and if it is safe to use in my reef tank as I have never seen rock that is completely red like...

Hi everyone I recently purchased some previously used rock that was left out to completely dry. A few of the pieces are completely red with white coats on them. They are easy to breaks apart and are even red on the inside. I was wondering what kind of rock this is and if these were safe to use...