If you see a man with a blow fish tattoo anywhere above his waist it means he likes to place male genitalia in his mouth. A common place for the blow fish is on the arm. This idea originated in Japan.
Person 1: "Did you see Justin's new tattoo
Person 2: "No."
Person 1: "It he got a blow fish tattoo on his arm! He didn't know that means he's gay!"
Person 2: "hahaha! What a douche bag!"