The only time I had a fish loss (my first year), it was the largest fish
that died. I was leaving for work, and my two biggest koi were floating. I
had an algae outbreak at the time (and other problems that aren't pertinent
to your problem). Oxygen deprivation will kill the largest to the smallest,
but you will find them floating in the morning with nothing to give prior
warning.

There are several "new things" in the koi world that will kill them: KHV
(Koi Herpes Virus) and SVC (Spring Viremia of Carp). Not to mention the bout
with BGD (Bacterial Gill Disease) that John Rutz just went through that has
decimated his collection. The fact that your fish died slowly is indicative
of a disease, not oxygen deprivation. I'm sure you've seen the mantra here
about quarantine, and this is why. It's time consuming, but it's worth it to
prevent the loss of your current pets.

Taking a big step into nowhere, I would venture to say that the first batch
of new fish were infected: they died first. The resident fish were
incubating. You mention that they looked fine externally, but that their
eyes looked "funny". "Funny" how - bulging or sunken?

Symptoms of SVC can include: bulging eyes, abdominal swelling, bloody mucus
from the vent, spider-web or skin hemorraging.

Symptoms of KHV can include: head down swimming, lethargy and weakness,
sunken eyes, gill lesions, sandpaper skin or a stringy slime coat, bloody
sores.

Not all of the symptoms need to be present: the above are "indications". You
didn't mention checking the gills: their condition will go a long way
towards diagnosis.

The incubating fish gave it to the new arrivals. To date, I haven't heard of
goldies contracting the diseases, but I've been concentrating my learning
curve towards koi, as that's what I have. I don't know if goldies can be
passive carriers, though.

Bugs dying of CO2 died from oxygen deprivation; I don't think they would
poison the fish. Contaminents from the yard were eliminated (you said you
don't use poisons). From my understanding, earthworms are pretty primitive,
and if they were sick or toxic, they would die pretty quickly. NEVER feed a
dead earthworm to the fish, but live ones are safe (or they'd be dead!).
Most airborne poisons would have done in your goldies, too.

If your water parameters were in shape, and your pond does not suffer from
oxygen deprivation (airstones are NEVER a bad idea!), I'd say you were a
victim to one of the above diseases. Please set up a quarantine tank: it's
much less painful than losing pets. The days of purchasing fish and turning
them loose in your pond are gone: the spectres of KHV and SVC are REAL.
Reports of these diseases used to be "isolated" a year or two ago; it is now
estimated that 50% of the breeders have been exposed. And it's growing
geometrically.

If there is anything else I can help with, please let me know.

Lee


"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.

None of the casualties showed any signs of bruises, parasites, fungus,
etc.
They just stopped eating, became listless, eventually had problems with
buoyancy, and died.

The two goldfish which have been in the pond for a long time still seem
fine.

To help analyze this and perhaps to serve as a warning, I will list the
steps which led to this end and recount all of the changes to the
yard/pond
made this year. If anyone can point out something, I would appreciate it.
I have a beautiful empty pond which I would love to restock with small
koi,
but I am a little afraid right now.

Changes in the Fish Community
1) I had 4 12' koi (raised in my ponds for 6 years) and a couple of 4"
goldfish in the big pond together for more than a year now. I had the big
pond built last summer as a home for the big guys.
2) About a month ago, I picked up 5 small koi (part of the deal I got with
my pond). I put them in my old pond with some goldfish for about 10 days.
These fish were not great fish, but they were free. Two died pretty
quickly
and the rest were very jumpy. But they looked OK so I put them in the new
pond.
3) The new koi all died in the new pond over the course of about 10 more
days.
4) Everyone left seemed OK so I added 3 more 5" koi (from a better
dealer -
these ones were not so jumpy and looked very healthy).
5) About a week later, I noticed that the big koi were not eating
normally.
Which is to say that they were not constantly ready to eat. Generally, if
you kept ladling food, they kept eating it.
6) The big koi died first then one died every other day - pretty much
largest fish to smallest fish (but only the koi). No visible parasites,
wounds, fungus, etc. although their eyes looked funny. They became
listless
and hovered rather than swam. They spent a lot of time at the bottom of
the
pond in the the heron shelter I built. At the end, the floated on the
top,
not moving at all (as if paralyzed), just breathing.

Changes in the Yard
1) Added more mulch around the pond (from a different nursery than last
year).
2) While digging in the yard, fed any earthworms I found to the koi (I
don't
use herbicides or pesticides).
3) Added a mosquito magnet about a month ago. This burns propane to
create
CO2. This was about 15 feet from the pond at a lower level than the lip
of
the pond. (Note: this is about 20 feet from the old pond which is full of
goldfish and has not had these problems).
4) I noticed that the pond has a frog visitor.

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.
2) The worms were toxic, leading to a slow death for the koi.
3) The CO2 plume emitted by the mosquito magnet created a CO2 pool over
the
pond, resulting in a low oxygen situation. The fish were gradually
poisoned
by the gas. The larger the respiration system, the faster the succumb.

Any Ideas would be appreciated, especially advice on how to safely start
over.

Thanks,

Rich in Chicago