Question
I have kept fish for many years, have an established 1000 gallon pond, koi dying weekly basis, had water checked, looks like type of   fungus. Treated pond with 5 day fungal treatment ,is it possible one fish infecting others, no fish eating as should , can you help

Answer
Dear Val,

Thank you for your question. It is correct that it is common for fish to infect the others.
Fungal can often be A secondary problem and often caused by A first infection like parasites, bacteria, wounds etc..
You need to let some experienced look at them by microscope to ensure the correct treatment.
Do you see the fish jumping, flashing or do they look like they are scratching or rubbing against walls, stones etc?

Best way to go is check it with the microscope (scrapes).

Good luck!
Warm regards,
Raf