Fish traps can be very useful in an aquarium as fish can be very hard to catch. A fish trap is an excellent method of simplifying this process which in turn causes you and the fish a lot less stress.
Most fish traps have a hatch door with a piece of fishing wire to keep it open and then when the desired fish enters the trap you simply low the door. It is often useful to put the fish's favourite food in the trap to speed up the process. | 
