how to prune Rhodactis mushroom and toadstool

[Pauper]

I have a very large Rhodactis mushroom, probably 8" or so and it's getting too big for my tank. I don't want to frag it but want to prune it down to size. What's the best way to go about this? Can I just use a pair of scissors and trim it all around?

I also have a large toadstool that's getting out of hand. How can I trim this without fragging it?