if all fail, try my method: leave a dim light in the room so that you can still see what is in the tank, turn off your main tank light, as soon and the tank light is off, the fish will try to adjust to the darkness, that is the best time to scoop it up, you got lesser than 15 second to do so, you can also use a flash light and shine on the fish face when he begin to adjust to the dark, the instant /quick bright light will mess their sense of direction.

Good luck, this method problably wont work with fish that goes in hiding when light off like blue tang. but it has work for me with various fish.

take some practice =)