Platies' Fin Types

Hi, I've got a rainbow wag platy whose tail just keeps growing! when I got him, he looked normal, but his tail fin has grown to quite a bit bigger than his friends. Since the new part of the tail is see-through, even though he's a wag platy, it's hard to see the new growth. It isn't causing him any problems, but it freaks out the other platies. So... my first question is, should I breed this fish, or is this a potentially harmful mutation? Do you guys think his tail will keep growing, or not? And also, what are some other cool fin types in platies that I should know about?
 
Thanks for the help!

Any pics?

Pics would be wonderful

Here is a picture. the new growth is the almost-clear section on the end of its tail.

Sorry it's sideways

Looks fine from that pic.

Ok. thanks guys! I will breed him and see if I can get this trait in more fry.