Hi,

I have a 15,000 gal pond with Shubunkin and Comets in it. I live in
New Hampshire, and the ice has finally melted back here. Water temp is
getting up to around 50, so Spring is in the air and the fish are on
the move.

Last Fall, I had a couple fish die unexpectedly. None of them seemed
to exhibit any problems until I found them dead, and one was a 6 year
old Shubunkin. Even after they died, they looked perfectly fine--no
fin damage, no visible sores, nothing.

At the time, I went into a panic and checked the water (it was fine),
and changed about 30% of the water "just in case." Unfortunately, due
to my water change, the salt I had added was basically rinsed out. No
other fish died, and winter set in.

Actually, to say no other fish died isn't entirely accurate. In May, I
added 14 mosquito fish to the pond on the advice that they were fine
for this zone. By the end of summer, those 14 had become about 1,000.
Seriously. They multiplied like crazy, and typically had 13 babies at
a time. I think they ate the goldfish babies because I didn't see any
more after the mosquito fish came. I had planned on having about 35
mosquito fish, but clearly they had other ideas. Well, as soon as the
water temp dropped into the 40s, all the mosquito fish started dying.
It now appears that they all died off. Since this happened at the same
time as the fish I just mentioned, I first thought there was something
horribly wrong with the water. But, since the water chemistry checked
out ok, I figured that the little guys died of the cold and the big
ones were just a coincidence.

So, now the fish are active again. A week and a half ago, I noticed a
Comet lying on its side. When I went to scoop it out, it swam away. I
had thought it was dead so I figured it was *almost* dead and swam
away to die. A few days later I saw it somewhere else, again on its
side. A few days later it was somewhere else. Every time I went to
net it, it swam away. Since it hadn't died on its own, I decided to
try to save it. For the record, over the years I've tried to "save"
probably 8-10 fish that were pretty far gone, and out of those 8
exactly 0 have survived. Call me an optimist but I keep thinking I'll
break that streak.

Anyway, I read up on the fish in my handy dandy "Koi Health and
Disease" book by Erik Johnson (most of it applies to goldfish as
well), and it sounded like the fish was suffering from gill disease,
probably due to flukes or something like that. I gave the fish a salt
dip in salted pond water, and then put it in a 5 gallon bucket of
unsalted pond water with aeration to observe until the next dip. The
book recommends giving the fish antibiotics, which I'd love to do, but
this fish wasn't eating and my local Petco doesn't sell syringes and
antibiotics. So, instead I put some Jungle Pond parasite killer in the
water and hoped the fish improved. After about16 hours, it was dead.
It appeared to have bled out since blood had seeped into all of its
fins.

Today, I noticed another fish on its side. This was another Comet and
again I figured the fish was dead until it started trying to get out
of the net. So, thinking that it's probably got the same problem as
the last fish, I gave it a salt bath like the last one and then put it
in a 10 gallon aquarium of pond water. I wasn't sure if the bucket was
fish safe, being that it was just a Home Depot orange bucket, and
since the last fish died so quickly there, I thought I'd avoid that
variable. I also decided to bring the temp of the water up so that the
fish's immune system would kick in. So I brought it up (slowly) to
about 60 or so with an aquarium heater. I also went to Petco and got
some Tetracycline to put in the water, since I'm convinced these guys
need some kind of antibiotics. And, again I put the Jungle Pond
parasite killer in the water. Since the fish was in a glass aquarium
this time, I could observe it better. Again, it looked completely
healthy except for its behavior. I *believe* I saw some very very tiny
thread-like things by the side scales of the fish. I can't be sure
though, it could have just been dust or something like that. Anyway,
after going from lying on its side to head-down-tail-up to head-up
just below the surface, it coughed up some blood and died. My record
of saving fish stands. Before I put anything into the water at all,
the fish had already gone to head-down-tail-up mode. It would still
swim once in a while, but it kept going back to that position. So, the
additives I put in the water didn't cause that behavior.

After this fish died, I pressed the gill covers open enough to see the
gills, and they looked (in my mind) completely healthy. They were
uniformly red and not blotchy--kind of like really lean steak if that
makes sense. One of them was really clamped shut, and I had noticed
that there wasn't much gill activity going on while the fish was
alive. I can't tell if this fish bled out in the same way as the last
because it's fins were orange, and I just can't tell if there's blood
in them or not. However, it definitely coughed up some blood.

I'm now expecting to lose more fish, whether I try to save them or
not. There's clearly something going on in the pond. After the ice
cleared and before the first fish I tried to save, I pulled out
another dead fish that was pretty decomposed. I'm not sure when that
one died but I'd guess it was a month or more ago.

What's confusing me is that the water continues to test fine for
things like PH, nitrates, nitrites, chlorine and ammonia and the fish
don't show any damage. They simply start lying on their sides and then
they eventually die. I suspect some kind of organism is in the water,
and for whatever reason I kind of latched on to the idea that there
are flukes in it, although I don't have a microscope to check for that
specifically. This is a large pond, but there are a lot of fish in it.
It didn't start that way, but the fish have been happy and populated
the pond. There's probably close to 80 or 100, ranging from 4" to 9"
tip to tail. It sounds like a lot of fish, but in 15,000 gallons with
6' deep for most of the pond, it's not crowded. I have an oversized
bead filter on the pond because of the fish load, although it hasn't
been running since the Fall. The fish that died in the Fall died while
it was still running.

I'm wondering what I should do to fix the problem. Actually, reading
this, I'm thinking I should get a microscope first and see if I can
narrow down the culprit. I do have some Trapdoor snails in the pond,
or at least I did last Fall. I suspect that they're down at the bottom
right now since I'm not seeing them and that's where I'd go if I were
a snail. The majority of parasite remedies kill off snails, and if I
have to do that, fine, but I didn't want to go that route until I knew
more. I'm leery of putting a bunch of chemicals in the water.

One pond skimmer ran all winter because I had tadpoles, frogs and at
one time mosquito fish in the upper stream. Keeping the waterfall
running was the easiest way to keep that from freezing solid since
it's only about a foot deep. This seems to have worked very well and
I've already seen tadpoles swimming about. The skimmer just feeds the
waterfall and I don't believe it changed the water temp dramatically
since it pulls from the top foot of water and returns via the
waterfall. The pond is over 6 feet deep everywhere except for a shelf
that runs around the edge. It has a bottom drain which goes to a bead
filter and UV light setup in my basement. That returns to the pond
through the waterfall as well, and that system has been off for the
winter. Only the one skimmer has been running. A second skimmer has
also been off.

Anyway, sorry for such a long post. I'm just so completely tired of
seeing these fish dying, I'm tired of thinking I can "save" them and
I'm tired of having them die all the quicker once I get involved. I
did buy some Fin-Quel last year for fish that clearly need to be
euthanized, but I didn't put these last two in that category. At least
not until I "helped" them.

If anyone can give me advice on diagnosing and treating the pond
problem as well as advice on better treatment of sick fish, I'd really
appreciate it. This is my second pond (the other was about 3200
gallons). This pond is two years old and aside from the mosquito fish,
I haven't added any fish to it since it was started. I've been ponding
for 7 years now, and most of the time I really enjoy it. Oh, by the
way, all the other fish are looking completely normal, are very
active, and are already bugging me for food. I have no clue which ones
will be the next to drop.

Thanks,

Dave