What happened around those towers was awful, Sissy. I sure would be raising some heck if that happened around here!!!
Here's what I do know: The kids fed the same food to both ponds, and they had a specific amount to feed daily. My fish don't eat any more than what I tell them, which is about 1/2 cup between both ponds, so about 1/4 cup of food. No way that was too much, and same food, so not the food.
I have not drilled the kids about if they had anything on their hands, but they are farmers, they raise hogs, they have to wash before going in or out of the hog lot, so they are VERY careful with diseases, and I'm not worried they had anything on their hands, they never put their hands into the water.
I don't give the dogs baths very often, and it's been several months now (I know, I'm bad ...), so that would not be it. The dogs DID get the flea/tick/worm pills and they DO drink out of the stream which feeds the goldfish pond, but I can't imagine that what they ate would have gotten into the water. But, good thing to think about.
The goldfish pond has a huge bog, no new plants added to it for well over 30 days (it's going crazy with what is in there, no room for anything more. LOL)
The koi pond has a bog, too, but only about 1/4 the size of the goldfish pond bog, and the water from koi pond does not exchange with the goldfish pond, unless I overflow the koi pond, then it overflows into the stream and DOES get into the goldfish pond. However, the goldfish pond water cannot go into the koi pond. So, again, koi are all fine, nothing looks amiss in that pond at all, just the goldfish pond.
Good news is no dead fish since beginning of the week that I have noticed. Did learn another new thing, as I had some fish dead on the bottom, others floating. Fish die and sink, then when they start decaying, they begin to float. Probably elementary, but I didn't know that. I wondered if they died from something different, as some were found floating, others sunk, and the guy told me that.
I have no idea if I should have done this, but of the 6 fish in the Q-tank, 3 were left in there, went through full treatment and water change, 2 of them were wanting food the last 2 days and swimming around, so they got put back into the goldfish pond. The last one seems to be struggling. Also, the 3 I put in a bucket of water to see if it was solely a water issue were just hanging in there at the bottom, not wanting to come up for food, so I put them in the Q-tank and treated it again (the 3 didn't go through the second treatment). Will give them 2 days, do a water change, see if any improvement. There are 2 or 3 fish in the goldfish pond that I see regularly at the surface, not really gulping air, but not swimming around like the rest.
Seems so strange to me ... how can some fish be sickly, others perfectly normal acting? And, I did a HUGE water change today again. Probably removed at least 25% again before adding fresh. The reason I don't want to do the slow change is that it would simply be mixing with what is in there, and I want to get as much of the water out as possible before putting new in, more of a drastic change than simply mixing it in.
Another thing: I thought frogs should have shown problems if it was a water issue before the fish, but I have tons of little bullfrogs in both ponds, and a turtle that has moved into the goldfish pond for the last week, and all of them are fine. So, whatever the issue is, it's just going after SOME of the goldfish. There are also 3 koi in that pond, and so far, none of them have any sickness issues. Baffling, to say the least!