Need help with diagnosing what is wrong with koi. We have a 2500 gallon pond with about 15 koi we treated a koi earlier this year for somewhat same symptoms but this guy is much worse missing most of top scales, have red and black spots, a large lesion on tail fin and a gooey substance growing out of Gill was milkish to color but after treatment starting to turn brown.
Pictures are koi in quarantine bucket.
Pictures are koi in quarantine bucket.