Remove mushroom

Scrape / chisel them off. They are difficult to kill. You don't need to worry about being too gentle.

If you are looking to more the mushroom to another location or tank simply cut it off the rock with a pair of scissors and put it in the desired place and put a mesh covering over it for a few days and let it attach there.  Another will grow back on the rock you cut it from in a matter of a few days to a few weeks.

If you are like me and you're thinking "I don't want that dang mushroom on that rock" and want to completely remove it you must find a way to remove every last speck of mushroom flesh from the rock.  The easiest way is by removing the part of the rock it is attached to, but easiest, does not mean easy.  Basically whatever you do if you leave any tiny trace of flesh on the rock it is likely to grow into a mushroom again.  They are basically like Aptasia that way only in my experience much more difficult to kill.

I wish I could be more help, but I'm currently loosing the mushroom battle myself.  The only way I ever had 100% success is to remove the rock from the tank and put it out in the hot sun or cold winter for a couple weeks.

Thank you for all your help, I cut them off and used tooth brush to clean of the rest from the rock. My rock is very big and not easy to move for chip off the mushroom. I will post with the update in few days.