What's the point of getting a dogs tail docked? So they don't knock things off the coffee table? Never understood people.
The bleeding heart tetras do just have random red shapes, just always in the same spot. There apparently is a 'true' strain of bleeding hearts. Where they found blobs very similar to heart shapes, bred them, took the heart shaped ones once the fry grew up, and bred them, and so on. Throwing in other heart shaped ones every generation for different blood.
Can't remember where I read that a long time ago.