I have my koi inside for the winter - mink problems.
I was away for 5 days and returned to 3 dead fish. Upon further investigation, I discovered that a number of the fish look like they have been eaten from the outside-in. I had my water tested and everything was fine. I took a fish to the store, and the only explanation they have is that they are eating each other.
I have one large fish - 14" or so, and a number of smaller ones (3"-8"). The large fish is fine. I have created a temporary divider to keep the large guy away.
I feed them daily for about 3-4 days, then I am often gone for 5-6 days.
Water is changed every 2-3 weeks.
Do you think the big guy was eating the others?
Is there anything more I can do?
Will the ones that still have chunks taken from them recover?
Thank you for any advice.