Some help please...cold water deaths!!!

[Brutuscz]

It is cold here in new england!!! The surface started to freeze and I have 2 large air pumps with 4 airstones bubbling just below the surface. Nothing new..have done it like this for years. Well..Today, I saw 2 koi laying on the bottom on their sides. I netted the first..and the gills were still moving. I brought him inside for my quarantine tank. Floated the bag..and dead within 2 hrs. Netted the second and already dead. Both these fish had survived the winter last season with no problems. I measured the water..ph=7.6, ammonia=0, nitrite=0. I add baking soda weekly to prevent a ph crash on my very soft water(gh40-60, kh-20-40). I have one other koi that doesn't look great....but all the others are fine. I've never had this happen at this time of year?? What the heck could it be??? I'm definitely at a loss.

[Russell Peters]

Quote: Originally Posted by Brutuscz It is cold here in new england!!! The surface started to freeze and I have 2 large air pumps with 4 airstones bubbling just below the surface. Nothing new..have done it like this for years. Well..Today, I saw 2 koi laying on the bottom on their sides. I netted the first..and the gills were still moving. I brought him inside for my quarantine tank. Floated the bag..and dead within 2 hrs. Netted the second and already dead. Both these fish had survived the winter last season with no problems. I measured the water..ph=7.6, ammonia=0, nitrite=0. I add baking soda weekly to prevent a ph crash on my very soft water(gh40-60, kh-20-40). I have one other koi that doesn't look great....but all the others are fine. I've never had this happen at this time of year?? What the heck could it be??? I'm definitely at a loss.

What are the symptoms of the other Koi? Is it covered with a light white coating?

[Brutuscz]

When I netted the 2 koi out of the pond..the others swam away rather quickly. This one seemed more lethargic...as if it was more difficult for her. It looked labored. When I put the 2 dead ones in a bag with water...there was a white slime that was on the surface. I thought it was a normal slime coat. No white coating on the fish though. What is the white coating you were thinking? Costia? ...any why now at below 40deg?

[koiscales]

Quote: Originally Posted by Brutuscz When I netted the 2 koi out of the pond..the others swam away rather quickly. This one seemed more lethargic...as if it was more difficult for her. It looked labored. When I put the 2 dead ones in a bag with water...there was a white slime that was on the surface. I thought it was a normal slime coat. No white coating on the fish though. What is the white coating you were thinking? Costia? ...any why now at below 40deg?

Did the fish feel dry or extra slimy? Costia is a fast killer and loves cold water. Scrape if you can and see whats going on.

KS

[Eugeneg]

Quote: Originally Posted by Brutuscz When I netted the 2 koi out of the pond..the others swam away rather quickly. This one seemed more lethargic...as if it was more difficult for her. It looked labored. When I put the 2 dead ones in a bag with water...there was a white slime that was on the surface. I thought it was a normal slime coat. No white coating on the fish though. What is the white coating you were thinking? Costia? ...any why now at below 40deg?

Brutuscz sorry to hear about your koi . Living in Canada this is a familiar story to me . You have to have a cover over your pond to be safe . Even then you should try and not let your temperature go below 42f for males and 46f for females . The koi should be in top shape before winter . Bubbler can move a lot of water so it might not be wise at times . Remember that at 36f water becomes slushy and koi have trouble moving their gills . If koi lay on their side it means a warning the water is too cold . What happened last year means nothing this year as the koi had probably grown 3 fold yet you did not expand your filtration or pond in the same ratio .
Regards
Eugene

[schildkoi]

Perhaps they were cold?

Steve

[Brutuscz]

I realized I left out a piece of information. It may be important. I had two of the airstones at the top, just under the surface. The other two were at the bottom. I just moved them up today. Could the two at the bottom have caused super cooling? I just thought of this.
I added a lot of filtration since last season..and more aeration.
I would be surprised at costia...I haven't added any new fish for a while. I quarantined all new koi and hit with form/mal green 3 times. Also with prazi.
I treated a few bacterial infections this year...but not too many.

[KoiCop]

Bob . . .

Two airstones won't supercool your pond although putting stones on the bottom will mix the water and disturb the warmest/densest water at the bottom of the pond.

Furthermore, if you've salted your pond that could add to the koi's winter stress?

It is important to point the affect of salinity levels on water temperature. We know from physics that fresh water under standard pressure and within bounds of natural salinity levels (.02 to .1 %) reaches maximum density at about 39 deg F. Ostensibly this means that a pond of proper depth and volume for a particular area of the country will not achieve water temperatures below 39 deg F at depth. We also know from physics that if we increase the salinity levels of the water, we lower the temperature at which water reaches its maximum density. This is why ice cream is made with salt and why salt water does not freeze at 32 deg F like fresh water. As temperate fish, koi will withstand water temperature down to 35 deg F before being affected by hypothermia and given this thin line of maximum water density (39 deg F) to the lower limit of 35 deg F, we can see that allowing an elevated salinity level (>.1 %) has the potential to cause serious problems with the fish's well-being. This fact needs to be considered when applying salt in cold water conditions whether to prevent nitrite poisoning or parasite control.
Source: REChttp://www.akca.org/kht/coldwater.pdf

What's more likely, however, is that the koi were stressed going into winter for whatever reason (shipping, crowding, parasites, medication, etc.), and just weren't able to handle your bitterly cold New England winter.

Perhaps a shelter of some sort would increase your margin of safety?

[Russell Peters]

Quote: Originally Posted by Brutuscz When I netted the 2 koi out of the pond..the others swam away rather quickly. This one seemed more lethargic...as if it was more difficult for her. It looked labored. When I put the 2 dead ones in a bag with water...there was a white slime that was on the surface. I thought it was a normal slime coat. No white coating on the fish though. What is the white coating you were thinking? Costia? ...any why now at below 40deg?

I was thinking sleeping sickness, it is a virus.

[Russell Peters]

Quote: Originally Posted by schildkoi Perhaps they were cold? Steve

This is a good point, sometimes they succumb to the cold.