Costly mistake!!

[Ross]

Hi all - during the recent severe cold snap my in-pond pump broke a the air line to an aerator disk forze which meant that my pond froze over as well as my filter [Nexus 300 Eazy] the ice was so thick that it was all I could do to keep a small hole clear to allow the gases to escape. When the pond did eventually thaw I found to my horror that 6 of my largest koi were dead but the 4 smaller ones had survived which surprised me as I would have thought that the smaller ones would have been more at risk.
I am now looking at building a new pond which will be heated to revent this happening again but just wondered if you think that my koi would have suffered?? A few people have said that it would have been a very painfull death for them and others have said that in really cold weather their metabolism shuts down and they would not have felt anything. Can you say which one is correct as I have never had a problem like this before in 7 years of keeping Koi.

Ross

[Lotusman]

Ross,
Welcome to KoiVet.

Your question has been asked repeatedly for years in the koi community. This has prompted researchers to tackle the idea and here are the results; it is inconclusive if fish suffer and feel pain. There are two bodies of evidence. Both have proven their point, so there is "proof" pro and con. The best way to look at this is to follow Dr. Helen Roberts lead. We professionals and amateurs alike should make the leap of faith that fish do suffer and feel pain, and treat them with the respect they deserve. Dr. Roberts regularly uses analgesics on fish, and is one of the few fish vets out there to do so.

[RickF]

There are really two parts to your question - the first, as Lotusman has answered, is whether fish feel pain.  The second is whether hypercapnea (increased CO2, which is most likely what caused the deaths) causes pain.  Increased CO2 concentrations act like a general anaesthetic.  Lethergy and somnolence would precede death; thus, it is most likely that the fish were sedated before they died, and therefore, would have felt no pain.

In cases where the CO2 concentration in the water increases, it is usually the largest fish that die first.  Without active aeration, a small hole in the ice is not sufficient to get CO2 out of the water.  It is easay to get O2 into water, but it is difficult to get CO2 out of the water.

[Ross]

Hi - thanks for your replies as i said the new pond will be heated so this wont happen again hopefully.

Cheers

Ross

[Lotusman]

Ross,
I think that once you get into what heating your pond will cost, you will consider other options. Several systems to vent the ice is always a good idea. That way if one fails, the other will still be working. A strong weather proof cover is another good option. Using a weather proof cover in conjunction with a water heating system is the best of both worlds.

[Ross]

Hi - my present pond is in the ground and has some large rocks around the edges so it would be very difficult to cover but I have decided that my new pond will be raised about 3 feet out of the ground and about 3 feet deep looking at 24 x 12 x 6 feet. I plan to use a gas boiler to heat the pond and will buy a cover for the winter. I know that the additional cost of heating will be quite costly but this year I have lost my 6 largest and most expensive koi worth over £2000 so heating the pond will cost less in monetary terms never mind the upset of losing your favourite koi.
Thanks again for all your help/advice it is most appreciated.

Ross

[koised]

Hi Ross

    I have a pond that is raised two feet out of the ground and is two feet in the ground.  One thing that I did was to put 1 inch of ridgid foam insulation on the walls to cut down on heat loss.  I also used a brick edge around the top to facilitate a temporary 2 inch foam cover in the worst of winter.  Using this the water never freezes even though I am in Michigan (cold side of Zone 5) with temperatures reaching -20F.  The down side is not being able to see my fish for a few months out of the year.  Perhaps this might be a less costly alternative.

[Ross]

Hi - thanks for your thoughts but I have already decided to do the whole thing properly this time and will definately be lining the pond with thermal insulating boards and then the whole pond will be fibreglassed. As I have already said this time I have decided that if I am to continue in this hobby then I will do things right from the start. I am even going to have a window on one side as a few of my mates have them and it is great to see your fish even when you have a cover on and they have told me where I can get the special glass from and then you have the stainless steel frame fibreglassed in position and the use a special sealant for the glass. Although I am still in the planning stage I am hoping to have the new pond up and running by August and I just cant wait.
Thanks again

Ross

[RickF]

I wish I could afford such a set up.  It sounds very nice.

One thing to consider is that koi do benefit from going through the seasons.  That does not mean that you need freezing cold or prolonged cold, but allowing the temperature to drop into the low 50s (F) for a month or so during the peak of winter is probably better than keeping it in the 70s (F) year round.

[Ross]

Hi Rick - I take your point and will be giving them a "winter" in january when I will drop to 11-12c for 4-6 weeks then slowly raising to 24c at the height of our summer then dropping again slowly from oct to acheive a smooth transition through the seasons.

Ross