My parents have an outdoor pond, about 8' x 4' x 2'. They had 6 large koi carp, all of whom have died in the last 4 weeks. They first started looking ill in July, recovered somewhat during August, and then went significantly downhill again in mid September.
Given that they were all 30-odd years old, when the first couple went, we just thought that it was the end of their life span, but now that all have died, there's clearly been a problem.
I've just taken a set of test results from the water
NH3 - 10ppm
NO2 - 0.75ppm
NO3 - 40ppm
PO4 - 5ppm
My logic is this something has clearly killed the filter bacteria. Had the ammonia just come from decomposition of the fish, then we would expect to see significantly more nitrite and nitrate.
The filter was relatively new - it was installed early last year, to replace the previous filter, which they felt wasn't up to the job, especially given the size the koi carp had grown to. There were no problems with it last year. However, as part of the installation of the pipework, my dad had to remove a brick, which took the brickwork at that point down to soil level.
What we think has happened is this The soil level of their next-door neighbours garden, immediately adjacent to the pond, is about 6" higher than soil level in my parents' garden. During July, we had a big load of rain, it was dryer during August, and then a fair amount of rain again in September. We think that perhaps the neighbour (who is a groundsman for Portsmouth FC, therefore knows a bit about grass!) used a feed-and-weed product on his grass, and the rainfall washed this out of his soil, down through the new hole in the brickwork, and into the pond.
The "feed" part accounts for the high phosphate level - the "weed" part would probably kill the filter bacteria, and make the fish ill as well. It never happened before, because of the relatively new hole in the brickwork.
Really, that's the only explanation we can think of, which matches the evidence, unless anyone has any other ideas?
And to go forwards, I reckon pump out all the water, somehow block that hole up, and refill with more suitable coldwater stock (the koi were stupidly big, way too big for the pond). Again, anyone with ideas, comments, etc., will be welcomed.
Given that they were all 30-odd years old, when the first couple went, we just thought that it was the end of their life span, but now that all have died, there's clearly been a problem.
I've just taken a set of test results from the water
NH3 - 10ppm
NO2 - 0.75ppm
NO3 - 40ppm
PO4 - 5ppm
My logic is this
something has clearly killed the filter bacteria. Had the ammonia just come from decomposition of the fish, then we would expect to see significantly more nitrite and nitrate.The filter was relatively new - it was installed early last year, to replace the previous filter, which they felt wasn't up to the job, especially given the size the koi carp had grown to. There were no problems with it last year. However, as part of the installation of the pipework, my dad had to remove a brick, which took the brickwork at that point down to soil level.
What we think has happened is this
The soil level of their next-door neighbours garden, immediately adjacent to the pond, is about 6" higher than soil level in my parents' garden. During July, we had a big load of rain, it was dryer during August, and then a fair amount of rain again in September. We think that perhaps the neighbour (who is a groundsman for Portsmouth FC, therefore knows a bit about grass!) used a feed-and-weed product on his grass, and the rainfall washed this out of his soil, down through the new hole in the brickwork, and into the pond. The "feed" part accounts for the high phosphate level - the "weed" part would probably kill the filter bacteria, and make the fish ill as well. It never happened before, because of the relatively new hole in the brickwork.
Really, that's the only explanation we can think of, which matches the evidence, unless anyone has any other ideas?
And to go forwards, I reckon pump out all the water, somehow block that hole up, and refill with more suitable coldwater stock (the koi were stupidly big, way too big for the pond). Again, anyone with ideas, comments, etc., will be welcomed.
