Koi skin issue

[Stuart1086]

Hi all,
I have recently built a new pond as previous one was too small, since adding my fish over a period of weeks I have noticed my large black Koi has developed some type of skin condition, any ideas based on my photos?

 

[Tula]

It is hard to tell from these pictures, but it appears to be a fungus .

 

[Mgessert]

I would rule out water chemistry issues that can damage the skin. Can you test for pH, ammonia, nitrite and nitrate? Might there have been chlorine in the new water?

 

[Stuart1086]

Thanks, if it’s a fungus how do I treat it? I will carry out the water tests.