The finger of suspicion therefore points at the copper water feature. I know that it is widely stated that one should not use copper in fish ponds, but a number of people we have consulted contradict this view (for example, an expert from whom we sought advice by email said "It seems unlikely to me that copper is likely to be the cause of death, as the fish survived/thrived for so long. The copper would be at its most toxic when new and less so over time as it becomes coated with lime scale and diluted etc."). A Salifert copper testing kit was used but it was difficult to get conclusive results as it doesn't really handle the low levels of copper that would be significant - but it did seem to suggest that there was more copper in the pond water than in our domestic tap water.


I didn't find the right solution from the internet.


- https://www.pond-life.me.uk/forum/viewtopic.php?f=27&t=15880

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