japanese coi

Question
I have recently cleaned out the pond. (filters, leaves and treated the water because it was completely black from over the winter) Three days later my 15 inch Japanese Coi is floating upside down, but is still alive. Why would it float upside down.

Answer
Anthony,                                                               I would like you to address this question to Robyn Rhudy.... he is an expert in ponds and Koi. You have obviously had him for quite a long time and want to make sure you get the correct answer.....Good Luck,Tina