Why are my fish dying this winter, but never before?

[MitchM]

Tough, you're right!
I have a feeling that because goldfish are so common, and bred in such high numbers that they have adapted more-so to the cold over here.

 

[crsublette]

Thanks Dave. Is that your friend in Ft. Saint John? They get pretty extreme temperatures up there. I'm not sure what the frost line is up there, but it's probably around 6 feet.
I have seen a number of koi, (Colleen's, for example) that seem to do well in ~32F waters. I've read where ice crystals forming on the gills of the fish is a real concern, yet we have fish that live long lives in near freezing temperatures.
I'm also thinking of that koi keeper in Norway that imported fish from Japan that did not survive. They don't get extreme temperatures there but the imported fish did not survive.
I'm going to try to find out where our local koi are raised next time I'm in town.

Yeah, there are just too many folk, such as Colleen and others, I have read about that have had koi in near absolute freezing water temperatures and never had a problem.
With a temperature range between -11*F (24*C) and -65.2*F (-54*C), I would imagine the frost line is insanely deep and ice accumulation on the surface would become quite thick. Also, with those low temperatures, it sounds like the region's Winters would be quite long. So, with long winter and thick ice cover with zero holes, I can see problems coming already due to poor pond management.
The theory of the "ice crystals forming on the gills" sounds slightly more reasonable of killing fish except I've never heard of this happening since ice crystals are lighter than water so they would accumulate at the surface. Also, if the fish were at the pond's bottom, then water above freezing would melt those crystals.
All I could find about "burning gills" is it being related to chemical dips, high ammonia, extremely high nitrites, or a pH crash.
CO2 is also heavier than water. So, if the water is not properly circulating, then there can be a thin layer of CO2 accumulation at the bottom. I am told fish generally are aware of these CO2 layers so they'll try to swim above it. Unfortunately, the warmest water is at the bottom on the pond. Also, these CO2 layers can create a pH crash if there is low alkalainity. pH = pKa + log([carbonate]/[CO2 dissolved in water])CO2 and carbonates don't have the same type of relationship as acids have versus carbonates. So, there could be a chance where the fish dips into this CO2 layer where the pH is noticeably lower. Once spring comes around and significant aeration is turned on, then this could cause serious problems if there was a noticeable CO2 layer allowed to accumulate at the bottom.
Fish through respiration and algaes and other biological organisms continue to release CO2 during cold temperatures in water at very low rates. So, in a very long winter without proper circulation and iced over pond lacking holes, I can see this causing serious problems to the fish.
It would be an interesting to read the article that supports the theory of cold water burning gills and the processes that allow it to happen.

 

[MitchM]

...
The theory of the "ice crystals forming on the gills" sounds slightly more reasonable of killing fish except I've never heard of this happening since ice crystals are lighter than water so they would accumulate at the surface. Also, if the fish were at the pond's bottom, then water above freezing would melt those crystals.
...
It would be an interesting to read the article that supports the theory of cold water burning gills and the processes that allow it to happen.

What I'm referring to there is the process of the water within the cell membranes freezing and the resulting ice crystals destroying the cell structure/walls. Same as frostbite. Very few animals are able to survive freezing of the cell structure. We have some frogs up here that can withstand it, but genetically they are built for that.

 

[crsublette]

What I'm referring to there is the process of the water within the cell membranes freezing and the resulting ice crystals destroying the cell structure/walls. Same as frostbite. Very few animals are able to survive freezing of the cell structure. We have some frogs up here that can withstand it, but genetically they are built for that.

Right. except... "freezing of the cell structure" indicates the water must actually be below the freezing point.
I understand frogs are also more likely to experience wind chill, which helps create the frost bite. So, I guess salt in water could be the equivalent of "wind chill" in water that causes the freezing point to be more easily reached ??.
Just not seeing the connection yet...

 

[MitchM]

No, frogs bury in the mud and the surrounding environment freezes solid. Antifreeze in their system and all that.
Arctic fish here have antifreeze in their blood but will still die after exposure to the winter air.
I'll have to look more into it to find what I did before on the freezing gills thing.
I get the feeling that we're really pushing the survival boundaries by only a degree or two with koi living or dying.
I would really like to find some answers though. Maybe there is some antifreeze showing up in the systems of locally raised koi.

 

[MitchM]

Here it is:http://www.koi-fish.com/koi-care/winter.html
Maybe Charles, you know whether or not it's a reliable web source.

 

[crsublette]

Here it is:http://www.koi-fish.com/koi-care/winter.html
Maybe Charles, you know whether or not it's a reliable web source.

Interesting. Thanks.
For me, the depth of explanation and references indicates the source's reliability. There's alot of bad info spread on the net so gotta be careful; just because it is on the internet doesn't mean it's true.

Make sure your water temperature doesn't drop below 34°F. If it does, ice crystals will start to form on your Koi's gills. Ice crystals can kill a Koi. Don't add any salt to your pond in the winter either. Salt lowers the freezing point of water, so if you add some to your pond, it could possible kill your Koi because the water temperature could drop below even 30°F.

Yep, that's what I figured. An extra contaminant would have to be present to reduce the freezing point. I have also read that as well about ice crystals forming just a couple degrees above the freezing point.
Yep, that makes sense, but the entire pond and the fish would have to be on those very cold water regions.
My assumption is not that the water is that cold at the bottom of the pond. Also, pond depth dependent upon the frost line as well.
Mitch, I figure you at least have a good quality 1500w floating or submersible heater to keep a hole open, maybe a couple of them, and so a deep pond's water at the pond floor would most likely be above 34*F. It would likely be closer to 39*F unless added contaminants changes the density.
I would figure proper pond management would dictate some type of good quality floating or submersible heater that is scaled to your climate.
Yeah, if it were up to me, I would never suggest allowing a pond's water to drop too much below 39*F. So, then, I would use some type of cover.

 

[crsublette]

However, 3100pond pond's is in Maryland, which is a 6b or 7a hardiness zone. Not for sure what the frost line is, but I am sure it is nowhere near as it is for folk further north. In my area, which is 7a, the frost line is only 8 inches.
I bet ya 3100pond's pond depth of 2.75~3 feet is just fine for his area as long as he is using a 1500w floating heater with an aerator underneath it, which is what I do and is probably overkill for my area.

 

[MitchM]

...
For me, the depth of explanation and references indicates the source's reliability....

..lol...
I don't know if you've read my pond thread, but I've recently added circulation to my pond and it's melting the big ice cube sitting on top.
I'm amazed that the bottom pond temperature is remaining at over 35F. That tells me there is a lot of heat available from the ground.

 

[crsublette]

Welp, if ya would read the proper material, then ya would not be surprised that your bottom pond temperature would remain over 35*F. I don't want to get into it too much since my purpose here is not to hijack 3100pond's thread.
Everyone has to find a way to judge if material is credible. Otherwise, you're bound to believe everything on the internet or everything written in books are to be the truth.

 

[MitchM]

I'm well aware of that, but I'm always interested how people interpret their observations.
(I'm not sure what welp means, I imagine it's a Texas thing...) :usa:

 

[Dave 54]

With two foot of ice over the pond and even the ir bubbles freezing it no wonder her koi ended up as they did.
Aince they have been taken indoors now during the winter she has had no more losses
Note the axe which was the only way to get through the ice she had to do it everyday if you also note the pond is under cover
It was even freezing around the heater that you can see in the second Photo and it was switched on 24/7 man thats cold !!!....
Further this Peter Waddigton the Author of koi kichi srares that the koi are used to a very short winter in their natve Japan , a long drawn out freezing as you get in Canada is a totally different type of winter, that for some of us is very hard to imagine here in the Uk weve only ever recorded -10c and that was my first ever winter outside with my koi heated
Her PH did not crash thars one of the first quetions I asked her .....

rgrds

Dave

 

[crsublette]

I am getting the impression that the heater was not properly sized since I would imagine, in that type of climate, the electricity cost would be quite high to have an outdoor water heater keep a pond at least 40*F (4.5*C).

I think there are too many other unkown variables to say exactly what killed her fish and the thick ice cover likely only exaggerated the current issues in her pond.

If there's anything to learn from her experience, then it is to take your fish inside if you cannot reasonably control the pond's environment.

I would think cost and space availability would be the reasons to bring the fish inside for winter, especially if in an area that has a long very cold winter. There would be a point where the cost of maintaining the pond outdoors would justify the expense of keeping the fish in a better environmentally controlled pond during the Winter.

Coleen's pond up in Canada (zone 2/3) does not have problems whatsoever keeping her fish in it during Winter, but I am getting the impression your friend's Winter isn't the same so sounds like it is a good idea for her to keep her fish inside.

 

[Waterbug]

Low temp is only one element in whether Koi or Goldfish survive a winter. That makes it very difficult to point to any one thing as a cause of death.

For sure I've never read anything that ever lead me to think there is any breed of Koi that can withstand lower temps. I'm not aware of anyone ever trying to breed such a Koi. The few Canadian Koi farms I know all use imported breeders to produce stock.

 

[Dave 54]

The strange thing is all her goldfish came through it was only her koi that succumed, each the same wat with all but the very top of their gills still red the rest grey and lifeless, as soon as the water warmed up they died.
I suggested we move them indoors during the winter months filters and all which she did, they now over winter in her husbands work place at 11-12c, since then she has not lost one koi.
Was she at fault:- no she knew what she was doing
Things that came to mind KHV :- no too cold
SVC :- no wild carp in pond to infect them so that was a no
We looked into gill flukes:- that was a no.
We also looked into sticky gills:- again no.
Water perameters :- no all came through as ok
which brings us neatly back to square one again the cold -24c with a windchill of -54c reported at that time......
The conclusion the intense cold had to be frying their gills but why did the goldfish come through un affected was it because they were smaller?.
Size was another thing they were all mature koi and around the 22" mark but the pond was big enough to to keep the koi in, maybe it was to do with the size of these koi: - Possibility?
Could it have been something to do with shock waves created during the hacking of the ice each day with that axe (only way to keep it open):- possibility but why then didnt it also happen to the goldfish?
In reality we went over everything we could possibly think of and drew negatives each and every time


rgrds

Dave