use a pint glass, and try to coax him into one of the lower corners of the tank, and try to get him in between the pint glass and the tank wall. This would be my first attempt to catch him before you start ripping stuff out of your tank.
Another method is to put a specmien container into the tank, without food, near the sandbed, and the fish can explore it for a few days. Once the fish become accustomed to it not being a trap, then place a small piece of food in there, wait for the Flame to take the bait, then close the trap up and catch it that way.