If you’re careful enough and don’t mind the gentle approach you should be able to slowly but gently prize them from any adjoining rocks which would enable freedom to remove and cut to new sizes if that’s what you want to. do .
If I could get to the stage of it being free from adjoining rocks I’d probably be inclined to remove it from the tank , cut it in half quick dip with reef dip of some sort , replace biggest back to original position and glue the off cuts to a new piece of rock and position them where you like or even sell them on if you wish to .
Just my thought to it .
Good luck what you decide to do ,
Very nice though