After 2 successful mini-spawnings this last summer (my first!) I was keen to get a better quality female. So on the weekend I visited a koi enthusiast who I had previously bought 3 fish from a couple of years ago. He used to have a beautiful set-up with three ponds and many stunning fish, but the thing is he has leukaemia and due to his illness is not able to properly look after them, so he took the step of moving all fish into his main pond. When I arrived I could see that the pond was clearly overstocked and fish were in poor condition and very listless. His explanation was that he had water issues and that the nitrate levels were way too high, which is further compounded by the severe water shortage we are experiencing in Cape Town (no water allowed for ponds, etc). Furthermore he confessed that about 20 of his fish had died in the past six weeks, and in fact there was a rotting carcass in the flower bed 2 metres from the pond.

Anyway, he gave (not sold) me two fish (approx. 30 & 60 cm = 12” & 24”). I could see that although to my untrained eye they were attractive, they were not in good shape - but the full extent of the injuries/disease only became fully apparent when I got them home and had a bit of time to study them. The smaller one has what appears to be a 9mm diameter ulcer in the centre of its back (which I had noticed earlier). The bigger fish has fin damage as well as an ulcer under the tail joint which I do not have a picture of, but which appears to be the worst wound of the lot. I took some pics with them still in the water which are a bit blurry, but I am trying to minimise their stress after having been relocated. For info I have them in a half full 1000 litre plastic holding tank with a decent pump/filter and lots of aeration. It has fresh spring water in with no salt added, and the temp averages around 20-22 degrees at this time of year.

Through trawling the www I have formed an impression that the wounds are probably bacterial in nature caused directly by the poor water quality. So my plan/assumption is that it may be best to keep them in quarantine with minimal feeding where I can better manage the water quality until there is some sign of repair/recovery. Common sense suggests that it would be better to fill the tank up to help dilute any waste etc, and I will try to get ion this tonight. But I would like to try clarify a few other issues:

Should I add salt to the water?
How long should the fish stay in quarantine? Ie why not release to the main pond asap (which also has pretty decent water)?
Lastly, has anyone had luck treating external skin ulcers? Will they heal up if left untreated? There seem to be so many different perspectives it is challenging as a koi loner and noob to choose one path over another. Another thread mentioned ‘Q-Tipping’ the wound. What typically would be applied? Could one use a human anti-bacterial product such as Betadene or would that negatively affect the water?
Will the fin damage repair itself? How long might this take?

PS - Please note that in spite of the fact I have only met him twice, I offered to go round in my free time to clean the pond, relocate the fish or do whatever possible to help. He said he would call me if it looked like he was not going to make it. All very sad.

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