Question
Hi. Hope you can help. Recently put 3 koi and one ghost (  some tench) in a temporary 'home' while their garden pond was being rebuilt. After about 1 week 2 koi died one night and all the other fish were gasping at the surface and the aerating pump in the temporary pool had clogged and failed. Tested all chemical levels in the water all OK so presumably lack of oxygen. Anyway, put bigger pump in - maybe too big - for 3 days and then returned fish to new big pond. They look OK but the large Ghost koi has changed colour dramatically. Was charcoal, now mirror scales all over! Can't be good news I guess but is it terminal??

Regards

Chris

Answer
I'm sorry.  It sounds like it was lack of oxygen.

Koi can change color with mood, health, or even just for no reason.  It's not as common as with goldfish for them to change color but it happens.  The stress of the changes may have sparked the change.  Scales themselves don't just appear but may change color or sheen.  If you send a photo to help at fishpondinfo dot com, I can tell you if the fish looks okay as far as color goes or if it appears to be a washed out or stressed fish.  If everything is good in the new pond, the fish should recover.  Good luck!