Depending on the size of the fish.... I use a soda bottle fish trap. If you can fit a two or even three liter bottle in your tank with some fishing line attached . Set it in and sit back and wait for the fish to explore it. I've caught tangs, wrasses and the evil evil damsel fish. Look it up on google. Very cheap and worth a try be for you buy an expensive fish trap
Just turn off all the lights at night and make the room completely dark when the coral beauty is swimming in the open and flash a red light and scoop it out since for a gpod 5 second it will stay in one spot.
This is how i catvh fish i want to change