I would recommend against the "death grip" strategy, however you can do what i do when I move large fish(10"-24"). Get a large clear bag(fishbag) and lower the water level of the tank, and slowly and calmly dip the bag in the tank and gently persuede the fish into the bag and lift up twist and tie. I moved many large fish including but not limited to a 20" silver arowana, a 16" red belly pacu, and a 24" royal clown knife. Went well with all of them