I have noticed air bubbles in and on top of my sand bed, particularly in one spot. I recently added a few sps coral to my tank and the bubbles are in the same area around the two corals. In this same area the sand on top is a purplish pink. My dkh is 12 my ph is 8.3, calcium is at 380 and salinity is 1.024. Can anyone explain this? Tank is roughly 3 mos old and I’m just as new to the hobby.