All my Koi are dying

[Flipp]

Hi extremekoi, thanks for your response. Yes I think you are right about the nitrite. levels.
The guidance I've received here has been fantastic and ensured that the same thing doesn't happen again.
The pond water is now clearer than at any time and I make sure to check water quality frequently.

What caused the water to go bad in the first place after 14 years without problems isn't completely clear the weather had been awful, I had added a new fish (without quarantine) and I altered the filter set up just prior to the problems starting so it could well have been the catalyst that upset the whole system.

Started afresh with a much better understanding and some of koimasters baby fish which are doing well