Koi fish not growing, sick or something else

[Tara]

I purchased these fish from the same place, same time frame all around the same size. The yellow and black koi has only grown a little, the others have more than doubled in size. He seems to act and eat like the others, but has remained tiny. I have noticed no odd behavior, lack of appetite. Is there something I should be looking for in regards to a problem, or just leave him alone, and see if he grows. These are the best photos I good get for comparison.

 

[Jhn]

if it is behaving normally and eating fine, I wouldn’t worry about it. I have koi that have been in my pond for 5-6 years and are a foot long. The largest koi in my pond is one that was born in the pond about 3 years ago it is roughly 18-20” long now. Genetics?, is it quicker to eat.....idk

 

[Jack B. Nimble]

Mainly genetics from what I have read, japanese imports grow very large and fast and domestic breed are slow and sometimes stay fairly small. Habit plays a role but, if some large same conditions I vote genetics.

 

[Tara]

@Jhn and @Jack B. Nimble thank you for the replies, was worried as summer is ending, hopefully it's genetics, and he has eaten enough to get though winter when it arrives. Maybe he will just remain smaller than the rest.

 

[Jack B. Nimble]

Your welcome and you probably know when to stop feeding at 50 degrees they cant digest.

 

[GBBUDD]

From what I have read, and from what I can see the fish I believe your talking about that has the black dot on the forehead is generally a domestic breed. the other three look more like traditional Japanese strains thus growth rate could differ greatly. Remember the short kid in school who shot up over the summer ? it may take him a bit longer to get a growth spurt

 

[Tara]

Your welcome and you probably know when to stop feeding at 50 degrees they cant digest.

I do, which is why I'm hoping he has fattened enough for winter.

 

[Tara]

it may take him a bit longer to get a growth spurt

I hope so, he was the same size as the yellow koi beside him.

 

[Jack B. Nimble]

I have seen brother and sister Koi and one can be 1/3 the size of it's own sibling at 2 years old. Just thoughts as well the other 3 may be girls and that is the only male which are also smaller.

 

[Lisak1]

We have the same kind of growth patterns - one of our fish is about 12 inches long; the others are 18-22". All purchased from the same supplier at the same size at the same time - genetics is my guess.

 

[Tara]

Thank you all for the replies, I will keep a close watch on him, if I feel like something else could be the problem, I will ask more questions. I can always think about bringing him in for winter, he just seems so little.