Two types one green probably gha other is super soft and slimy and brown
Tank just cycled so I’m expecting this but would like to know any solid way to remove it ASAP could be
I want to say possibly cyano, but with the tank just going thru the cycling stage it is more than likely the ugly stage and will go away on its own as the tanks bacteria builds. You can blow it off the rocks with a baster, but it will come back.