Can someone tell me what this is? Its constantly on my rock wall and border. 5 to 1 diluted MA reacts with it a little bit, bit doesn't seem to clean it very well. (I'm not sure if its just reacting with the soft stone or if thats possible though.)
Anyway to clean this off and keep it clean? Here's current numbers as well.
Ph - 7.6
FC - 6
CC - 0.5
Salt 3200 (Reading from K-1766, SWG Reads 2900)