Hello everyone I am pretty new to the hobby only had my tank running for about 6 months. For the past 2 months my sand bed has had a brown coating on it. I didn't care about it too much as i would stir it up and syphon most of it out but it is now growing on the corals and they are having trouble opening. If anyone can identify what my problem is and how to get rid of it that would be much appreciated.