How come one of my fish's fins is bigger than the other

[BennyLava]

I have an orange butterfly koi that is probly a foot long. One of his fins on his side is clearly bigger than the other one. I don't like this. Is this some kind of genetic abnormality? Or is it just cause one of his fins got bit off by something and now its growing back?

 

[addy1]

I have an orange butterfly koi that is probly a foot long. One of his fins on his side is clearly bigger than the other one. I don't like this. Is this some kind of genetic abnormality? Or is it just cause one of his fins got bit off by something and now its growing back?

Could you post a picture, it might help them figure it out.

 

[BennyLava]

Man I'm not sure if I can catch that guy. I can say this though. The little fin looks pretty much perfectly formed, its just about half the size of the other side. Its not all tore up or anything.

 

[addy1]

If it was my fish I would just watch and observe what happens, sounds like it might be growing back out. Maybe damaged at some point.

 

[fishin4cars]

It's not that uncommon for Butterfly Koi to have fins of different sizes. I'm guessing it's genetics. In small fish under about 8" it's not as noticable but as the fish grow larger it stands out more and more. I have one that is doing the same thing and I saw one at the Koi show this last weekend that was the same way and the owner was selling the fish due to the fins were different sizes. Nothing health wise is wrong with them except the fins look way off in proprtion to size and makes the fish look off balance.

 

[BennyLava]

Yeah I went to a koi farm and saw a plenty of butterfly there that had this problem. The fish is only about 13 inches long right now, but if its not gone by the time he gets to be about 20" then I'll probably trade him off or something.