One quarantine tank filled with about 10 kois size about 50 - 72 cm Dick. I didn't feed them at all, only once of 2 weeks with small amount only. I acknowledged that the stock may too many for the quarantine tank, that's why I didn't feed them to avoid ammonia, nitrate and nitrite rising.
Lastly I found that some kois had fungus on their body and head area, so I tried to cure them with 3% salt + teramycin. 3 days later, all kois were just get okey then I changed the water about 30% to flush out the antibiotic waste. Then a week later I found 2 of the kois having fungus back again and I did the same medication to them, and last night was the 2nd night but I found all the kois breathe hardly. The water had many bubbles and I quickly test the water and found the pH down to 2,8 while TDS hit 500+. I just don't have any idea what was happening.....