First Koi death in this pond. Pond is about 7 years old and this was the first fish purchased. Noticed the fish isolating itself from the rest of the group 3 days ago. Tested the water and here are the following parameters
Ammonia:0
Nitrite:0
Nitrate 5ppm
Ph: 7.0
No ulcers, no lesions. Just slow swimming.
Came home today from work and found laying on the bottom of the pond. Pulled up the koi and noticed excess mucous near gill areas. Opened the gills and they were not red, rather white/grey in color.
Tested the water again tonight and same results as previous.
All other koi are very active and show no signs as the yamabuki.