I went through a similar experience after purchasing goldfish from and on line vendor but they were being held in quarantine in a 400 gallon pond when they started displaying nearly the same symptoms and resulting death. I determined that my fish were suffering from some unknown parasite. I used Proform C which is a broad spectrum malachite green & formalin treatment which will eliminate nearly all parasites that afflict goldfish or Koi. Read the directions carefully and treat your whole pond three times doing water changes between treatments. Worked wonders for me and came very highly recommended at that time. I tried salt myself and they still kept dieing since salt is only effective for a few parasites why waste your time. Once treated as prescribed you will not need to drain the pond since all parasites should be eliminated. It is important to have a fairly accurate knowledge of the volume of your pond. One quart will be enough with plenty to spare. Let us know how it all is resolved.
I was so happy that I quarantined these fish and not released them into my main pond of 8000 gallons with many other fish until I determined they were healthy and free of parasites.

Hi Adrienne. The first thing I do if I've heard that someones pond fish are behaving this way is to make a one third water change from the bottom of the pond to remove excess toxins from the water which seem to be buring the gills due to excess ammonia in the water.

Your's Koily, Lorraine

I'm sorry that you learned the lesson to always quarantine new fish the hard way. Well known or not, many pet stores have diseased, parasitic or dead and dying fish for sale. You can't always tell there is a problem by looking at them and they may not know either. Best to always quarantine new fish in a different pond or aquarium.

Yup, it's a hard lesson. Guess I've always just lucked out before, made me too complacent. I feel bad for the victims!

I'm going to try frogman's suggestion of Proform C - won't hurt and may very well help alleviate any parasitic co-stressors. And then I'll have have some left over to use in my future quarantine tank. Bonus. Thank you frogman.

And thank you too Lorraine. I did do a partial water change a few days ago from the very bottom of the pond, that was how I knew there was little debris. I've also always tried to make sure that there were minimal stagnant areas in the pond by spacing the skimmer, pump, little waterfalls and spitters around the periphery. My nitrites and nitrates have always been essentially 0. Do you mean that the fish can still get ammonia burns with readings like that? Uh-oh, didn't know that.

I took pictures of today's casualty earlier along with a fish who I suspect will go in the next couple of days. Any feedback you give me about what you see or things I can improve on will help me know what to look out for next time.

Here is a link that might be useful: sick fish

Your test kit should include an Ammonia test. The strips are not very reliable, drop test are much better but what ever you have test it.

Silly me. I just double-checked the types of tests that I have. The strips which I use every few days for a quick dip-and-see DON'T include ammonia - my more elaborate master kit with the drops does. I had never noticed that discrepancy before. I only use the drop tests before I do my water changes because of the relative time and expense - but it is fun for the neighbour kids to help me with my "chemistry experiments". I think they all love the pond as much as I do! For my peace of mind, I did a full test today and the NH3 level is still 0 today. Phew.

And I've been wondering too about the dissolved oxygen level of the water. Is there a test for that as well? I think that I'll just put a couple of bubblers from my currently unused aquariums into the bottom of the pond...just as a trial.

I should also go read up again about the entire nitrogen cycle. We may never stop learning but darn, I wish I could remember everything I have already studied!

Adriennemb,
It is had to say from the pictures but if I had to guess I would say you have ick. Proform-C will clear it up. Goldfish die quickly from Ick. It also looks like you have some bacteria infections going on.
Mike

The last of my original goldfish died today. Darn it. I'm guessing that it was altogether too late for the Proform-C to be effective. And Mike, you were right about the ick. There was absolutely no sign of it with the earliest deaths, but all the last fish were definitely affected.

What I find interesting is that the snails, minnows and the two remaining shubunkin culprits (from the pet store) seem totally untouched - yet. And there are still fry, some newly hatched and other older ones about 1" long. I think that I'll just leave it at that for the rest of the season and start fresh in spring.

I do want to thank you all for your help. It's been a real learning experience.

Fish can become immune to ich. So the fish that brought it into the system have some immunity and everyone else dies off so does the ich, leaving your original shubunkin.

An ounce of prevention is worth a pound of cure.

I keep all new fish in 3 parts per thousand salt as that kills many ciliate. The proform C would be a good quarantine treatment, better in quarantine than the pond as it is very toxic stuff. Keep your pets away from it.

Praziquantel is also a great thing to treat with. Very low toxicity and very specific treatment for flukes. I treat every thing atleast once if not 2x a year with prazi.

Sorry you lost your fish.

Best fishes
David
www.goldfishgarage.com

Thank you David. I very much appreciate the info. The minnows and snails are thriving, all the previous fry are dead. So do you think that the remaining two shubunkins will still be "carriers" despite treatment 10 days ago ? They are still healthy, even mating. If there are resulting offspring, will they die from ick as well or do you think enough time has passed?