Yes. The STONEFISH, Good luck getting ahold of one, and it would kill anything in your tank but yes IT would defeat your mantis shrimp and take the aqua-proverbial crown.
look for it on wiki. It is the most poisonous fish in the world and lives on the ocean floor looking like a harmless Rock. A harmless rock that would make you wish your arm could be amputated after a sting.
