Pink Sea Turtles are make believe animals. They cost 25 pearls. They can mate with Green Sea Turtle or Green Turtle with Pearls or Facebook Credits. After that, the Happy Aquarium Company removed the Credits Costing.
The Offsprings can be a Rainbow Sea Turtle, Orange SEa Turtle, and Periwinkle Sea Turtle.
There is also a Male Pink Sea Turtle, but you can more of get via the premium gift that a friend should get for you.