Help my Koi!!

[Lisak1]

Without knowing what's causing the problem I wouldn't be treating the whole pond. But that's just my opinion.

 

[Mmathis]

Without knowing what's causing the problem I wouldn't be treating the whole pond. But that's just my opinion.

Agree, and share that opinion. But it’s almost surely a water quality issue — but it’s the kind of issue where you do a complete reassessment of your husbandry.