Red streaks on koi fins, small white patches. What’s going on?

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OliveFish05

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We have a 1,500 gallon koi pond with koi and goldfish. The goldfish all look fine, the comets and the fancies, but the koi have bloody red streaks and patches in their fins. Some of them are rather tattered. Several of them developed excess slime coat on their fins, now some of them have white patches, almost like very large grains or small nodes. It is not ich, it is much larger. In addition, about 3 of the koi developed grayish grows on their heads or faces. The ones who did the worst, we brought inside and quarantine them in stable temps with 80% water changes every other day, and they healed right up. I know this sounds like “water parameter issue”. Just checked with an api liquid test kit, no ammonia, no nitrites, the nitrates are barely registering.

I am totally stumped. I am guessing it is something to do with the inconsistent spring temps? The temps dropped from 70F to 20F overnight last week. 50 degrees in less than 10 hours. We lost 6 koi in the cold snap, I’m guessing it was extra hard on them because of the very recent stress from my uncle’s koi?

But anyway, thoughts?
 
It seems more like stress. I don't own koi anymore but I've kept and bred them from the mid 1980's until 2005. But when they were stressed the same symptoms appeared. Especially, when the season changed from winter to spring. But after 1-2 weeks they turned normal again.
 
It seems more like stress. I don't own koi anymore but I've kept and bred them from the mid 1980's until 2005. But when they were stresses the same symptoms appeared. Especially, when the season changed from winter to spring. But after 1-2 weeks they turned normal again.
That is so good to now! That’s definitely what’s going on here. All the flowering bushed bloomed a couple days ago, and the weeping cherry trees bloomed last week. Is it normal that some are struggling more than others? We lost 6 in the cold snap, it dropped 50 degrees overnight. Is this normal? We have two who are struggling still... the others, especially the larger ones, are just showing the signs on their fins but no lumps or growths, and not super lethargic.
 
That is so good to now! That’s definitely what’s going on here. All the flowering bushed bloomed a couple days ago, and the weeping cherry trees bloomed last week. Is it normal that some are struggling more than others? We lost 6 in the cold snap, it dropped 50 degrees overnight. Is this normal? We have two who are struggling still... the others, especially the larger ones, are just showing the signs on their fins but no lumps or growths, and not super lethargic.
Not all koi are having the same level of health condition. So yes, this is normal. But it's got also to do how deep they were resting in the pond. The ones that didn't stay very deep during the cold, have most problems to get through it. Because the temperature difference was the highest when you come closer to the surface.
 
Ohhhhh ok. It is definitely the smaller ones struggling the most. Is there anything we can do to make it easier on them? At this point, the temps are gradually rising, a degree or two each day.
 
Red lines (blood) in the fins and cream white patches on the fins is poor water quality.

Lumps or nodules on the fish (the same colour as the fish) can be Koi Pox (a herpes virus) that is stress induced and usually goes away when conditions improve. However, if it is Koi pox, your fish might catch it.

You can do a big water change and then add some salt to the pond. It might help. Otherwise monitor and see how they go.
 
Red lines (blood) in the fins and cream white patches on the fins is poor water quality.
Poor water quality, how? Like toxins in the water? The Ammonia and nitrite are 0, the nitrates are less than 5 ppm. The plants are all starting to come back.
 

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