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Safe Haven for Koi Carp in winter

Safe Haven for Koi Carp in winter

Safe Haven for Koi Carp in winter

(OP)
Hi All,

In order to prevent our koi from experiencing dangerously low (less than 5 degC) temperatures in winter, I am thinking of creating a safe haven for them within the pond in our garden.

The idea would be to build a box out of insulated board (such as celotex), say 1m square with a height of 0.5m, with an an opening on one side large enough for the fish to enter and leave (say 0.2m diameter), which would be anchored near the bottom of the pond. The box would have an electrical aquarium type heater, with the thermostat set at 5 degC.

To ascertain whether or not this is feasible, I am looking for an equation to model this situation, which calculates steady state conductive heat loss from an isothermal body (in this case a disk of 0.2m diameter) at temperature T1, which is exposed on one side to a (semi-) infinite volume of water at temperature T2. Worst case would probably be T2 of 2 decC with T1 at 5 degC. For sake of simplicity, I would also assume that there is zero heat loss across the insulated walls of the box.

Would really appreciate if anyone could help with this.

Cheers

Big Vern, Leatherhead, Surrey, UK

RE: Safe Haven for Koi Carp in winter

What USDA zone do you live in and how deep is the pond.
When we lived in Indianapolis our neighbor had one end of his pond 3' deep.
The mud protected then fine.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Safe Haven for Koi Carp in winter

Are you sure koi can't live in 0C water? They are carp, after all. Carp live everywhere. I would think as long as you aerate, the fish would be fine.

RE: Safe Haven for Koi Carp in winter

(OP)
Thanks for your responses guys. I live in Surrey, UK (can't find a decent forum here!) and we have just had a relatively harsh winter, including zero temperatures. Our pond is deep enough at around 4 ft max to stop a total freeze, although we do get an inch or two of ice on top when its really cold - except for the area where the filtered water comes back into the pond via a water fall which also aerates and keeps this part of the pond ice free. BTW, there is a lot of info on the internet about possible stratification of water layers in a pond and, although it's fair to say that the deeper layers will be a little warmer in winter, due to circulation, the difference is relatively limited so, digging a pond much deeper doesn't really make much difference - although the bigger the volume will of course reduce the rate of the overall temperature change. In such conditions, our fish normally just rest on the bottom but, this year, three of our koi carp died, although I managed fortunately to save another one (around 18" long) which was in distress with the help of a local specialist, who advised that I bring the fish inside the house. Initially, the fish was in our bath tub, but was then transferred to a koi bowl (4ft diameter, 2 ft deep insulated container with filtration system and aquarium heater. Koi are indeed a type of carp, as are gold fish, so are pretty tolerant of temperature swings., However, because of the inter-breeding that has occurred over many years, koi do not have the same tolerance of other carp species and their immune system pretty much shuts down once they get below around 4 degC, so are vulnerable to all sorts of ailments at such temperatures. In our case, according to the local specialist, the koi were suffering from chilled swim bladder, meaning that they lose the ability to hold their position in the water - which is why in our case the fish ended up floating on their side on the top of the pond. When I brought the fish inside and gradually introduced it ton warmer water (max 2 degC increase per day) it gradually recovered and after around 3 days was back to normal. The bottom line therefore, is that I need to keep our koi above 5 degC.

RE: Safe Haven for Koi Carp in winter

Twer me.. I'd go more drastic. I'd run an insulated loop out from a GAS hot water heater using a thermostat to run the circulator pump, keeping the water at whatever temp you feel you need. I'd cut a pool cover to fit the pond leaving an opening to feed them and for gas exchange. The pool cover will help prevent the hot water from needing to circulate if any sunlight comes out as it will help trap the solar gain.

Use the whole pond as the thermal space and not just a box. The carp could avoid the box as a dark hazard. They could also run the oxygen way down if they actually did hang out in the box.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Safe Haven for Koi Carp in winter

Put a glass or clear plastic cover over the pool and convert it into a green house. That should make enough degrees difference to keep the fish warm enough.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Safe Haven for Koi Carp in winter

For swimming pools they use thermal covers that are basically heavy duty bubble-wrap.
They provide some insulation and they allow some solar gain.
Floating that on the pond my do the trick.
And then if you still need to add heat it will help trap it better.

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P.E. Metallurgy, Plymouth Tube

RE: Safe Haven for Koi Carp in winter

Man, that's awful. surprise

RE: Safe Haven for Koi Carp in winter

(OP)
Many thanks for all your thoughts guys! I've already been thinking about bubble wrap, but hadn't thought of making a plastic or glass cover. It's a fairly big pond (around 45ft by 30ft) in an exposed area, so I would have to use some fairly strong and well anchored material. It is however already covered with a heron net held around 3ft about the water by metal posts around the edge of the pond (essential where we live since these birds were granted protected species status!). I could therefore get some heavy duty clear plastic and drape this over the heron net and anchor it around the edges with tent pegs. I would set this at an angle of 45 degC max from the ground around the edges so the wind will blow over rather than against the sides of it. I did also think about using our gas central heating system and, whereas I think that the operational costs might be acceptable, especially if the pond surface is insulated in some way, I was put off by the capital cost, as well as the work required to bury the insulated piping as the pond is around 260ft from our boiler. Lastly, I also note the points Keith makes on the likelihood of the koi avoiding the darkened box in the pond and would run the oxygen level down - so will bin this idea.

RE: Safe Haven for Koi Carp in winter

I'm sure I've told the story of a coworker's Oscar... what started as a fish the size of two fingers ended up eating lizards (anoles) and such from our hand by jumping out of the water to grab it. He got... big.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: Safe Haven for Koi Carp in winter

Yea, and the clear plastic would also provide you with some 'greenhouse' effect to keep things a bit warmer than the ambient air temp.

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

RE: Safe Haven for Koi Carp in winter

My dad has a small koi pond outside in Minnesota. He didn't lose any of his fish following the first winter. I think the issue bigger than the temp is if the oxygen level gets too low due to the ice cover. I believe in Minnesota for fish in the lakes, the DNR will sometimes takes steps to oxygenate the lake if the oxygen levels get too low.

RE: Safe Haven for Koi Carp in winter

Or find some swimming pool thermal cover and let it float on the surface, and anchor it to the base of your stakes.
Yes, predators are a big issue, both birds and various critters.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Safe Haven for Koi Carp in winter

(OP)
Many thanks for the further helpful comments guys! Oxygen content is indeed important, as is the need to keep the ammonia, nitrite, nitrate & ph levels within limits, so I keep the filtration system running year round. The water returning from the filters tumbles back into the pond via a waterfall, so this both aerates and keeps a fairly significant part of the pond ice free. I can see pros and cons of either suspending clear plastic above the pond or using a pool type cover on the surface of the water and I think my final choice will be made on a comparison of the cost as well as the durability. Fortunately, it looks like spring has finally arrived here, so I (hopefully!) have until next winter to sort this out.

RE: Safe Haven for Koi Carp in winter

Have you considered a water trough heater?

RE: Safe Haven for Koi Carp in winter

We had a much smaller pond growing up in Hampshire and one severe winter the ice on top got about 4" thick and several of our large Gold Fish (and I think one random Koi genesis unknown) got caught in it as did a frog if memory serves.

In terms of throwing a plastic sheet over the Heron netting, does your netting have a suitable pitch to it so that precipitation won't collect. Even with pitch any snow might be an issue. I'd also be a bit worried about wind unless you can anchor it really well.

If memory serves the water at the bottom of a cold pond will normally be at least 4°C because the peak density of water is at this temperature. So if your confined region can be kept on the bottom of the pond you're only looking to heat it a relatively small amount.

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RE: Safe Haven for Koi Carp in winter

We have a shallow (2ft. deep at it's deepest) goldfish pond. It's about 400 gallons.
I'm in central Indiana.
We have bubblers, and a trough heater, and have never had issues with our goldfish or koi.

On the subject of the catfish... we also have a large channel cat in there, and have never had a problem with him eating other fish...
I have always had catfish in my ponds. They may go after the babies, though, and get them before we even realize they're there.

David
Connect with me on LinkedIn. http://lnkd.in/fY7-QK
Quote: "If it ain't broke, I must not've fixed it good enough"

RE: Safe Haven for Koi Carp in winter

(OP)
Many thanks for the additional comments guys! You have an excellent forum going here, as I never expected so many helpful responses.

RE: Safe Haven for Koi Carp in winter

Thank You for the kind comments about our forum, Big Vern and welcome. You are one of us now.

Bill
--------------------
"Why not the best?"
Jimmy Carter

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