How Do I get rid of Koi Fish Fin Rott?

Question

Ok so ive had a holding tank for koi for some time now. Recently i think i bought a sick fish which infested and killed every single one of them. So the tank has been empty for 3 weeks. Recently i put in 2 two inch kois which were very alive and healthy. One of them started growing fungus a week later and died. The second one seemed fine till today i noticed fin rott.

Could a disease stay in a tank even when its been empty (nofish)?

Its only 1 fish and i plan on healing it so any medicine recomindations?

Also i know koi are pond fish and dont belong in a tank. blah blah blah i dont need to hear it.

Answer 1

Did it maybe occur to you that the reason your fish are continually sick is because they are in a tank?  In a pond, they'd have enough water to dilute their waste, but in a tank (unless it's several hundred gallons), their waste builds up quickly, stressing them and making them extremely susceptible to infection.  Until you get them into a massive tank or pond, you won't be able to save them regardless of what you do.

Answer 2

Diseases area sign that your water quality is less than good.

I'd suggest changing 50-75% of the water in the holding tank.

Also, invest in a liquid test kit to test for ammonia, nitrites and nitrates. If those levels get too high, your fish are more likely to die. .25 parts per million(PPM) is the max for ammonia and nitrites. 40ppm is the limit for nitrates.

Answer 3

as you have stated you kois are very stress is your holding tank well aerated?   rock salt with mythelene blue and don't feed them yet for 3 to 4 days.

Answer 4

there is medication for fin rot, it contains formalin and malachite green