Mushroom Trimming Question

[BigHildy53]

Are there any risks in trimming this green mushroom(?) thing? I truly don't know what it is. It's one of the few things growing constantly in my tank. Just want to make sure it doesn't release any toxins. And what is it?

 

[BigHildy53]

I'm changing my question to, what is the best way to remove the mushrooms from the rock. I thought it would be easy to just cut the mushroom off. Not that easy.