"Richard C. Eberhardt" wrote in message
...

Well, all the koi are dead now: the pretty 12" ones I had for six years
and
the 3 new ones added this summer. They seemed to die one at a time, from

largest to smallest animal.
My Ideas
1) I introduced some strange koi disease with the new fish. It would be
something that does not leave a mark and strikes the largest animals
first.

I am sorry to hear of your disaster. I doubt the mosquito magnet had
anything to do with this. It produces CO2 and pheromone, attracting
mosquitos to the device for trapping. It does not disseminate poisoned
insects. I would favor one of two possible explanations:

1. Your first choice above. You have a long record of successful Koi
raising, and this seems like the most likely source.

2. Even though you do not normally use pesticides, is it possible for your
neighbor's lawn care product to have been washed into your pond? How about
rose dust/spray. Any fruit trees in the area being sprayed? Spray can drift
a fairly long way, particularly under windy conditions. Did your community
spray for mosquitoes in an effort to prevent West Nile? That said, however,
I would expect the smallest to die first of poisoning.

I would buy a couple of new fish, keep them in an aquarium or child's wading
pool for a couple of weeks of quarantine, and if they are healthy after
that, introduce them into the pond. I would also test the water prior to the
introduction. The survival of the goldfish suggests that the pond water is
not grossly bad.