Being my first SW tank I am having a hard time identifying what is what. Originally I thought these patches were coralline because they would pop up random places on rockwork only throughout the tank and actually seem to be growing best in high flow areas. They also dont scratch off easy but if you rub hard you can start to rub it away. As they get thicker its almost like they have a little bit of a fuzzy appearance but not slimy or smooth. I question if it is cyano since I used tapwater and my nitrates are 5-15, also tank is only 2 months old and I know this is common in new tanks and when using tapwater. What am I dealing with here??