For very powerful heaters check out http://www.KoiFishPonds.com/pond_heaters.htm
At the beginning of December 98 we had 60+ days, but our nights were cold, usually 35 - 40, with many in the 20's and one down to 13. The pond temperatures were usually 50 in the morning and the sun would heat it up about 4 degrees to 54 in the late afternoon. I decided to try a submersible 1000 watt Titanium heater with an electronic thermostat which I left in the box. The mfg. of the heater is TitronX and it retails for $75, we can supply them at a discount if you can't find them locally.
Since it is a 1,000 watt heater, it consumes a kilowatt per hour or 24 kilowatt-hours per day. If you are paying about .08/kilowatt-hour, then the cost is almost $2 per day, or $60 per month. The manufacturers recommend about 4,000 watts for a 2,000 gallon "indoor" aquarium. I considered buying 2-3 more, but I couldn't see spending $240 per month. It would be cheaper to use a full blown gas heater with a separate water pump and piping.
The fountain pump is a "Little Giant" that pumps 4,100 gallons per hour and all the flow we need at the 14 foot high top. It uses 700 watts which costs about $42 per month to operate at .08/kilowatt-hour. We operate it year round but turn off the top two bowls for the winter.
We also have a floating 1,000 watt de-icer that is supposed to come on at 35F and turn off at about 40F. So at times the fountain was pulling 2,700 watts.
I had several reasons for heating the pond. First, I had some very small Koi, only 3" and I was trying to make sure they survived the winter. Second, I wanted to make sure the ice didn't push the walls out resulting in cracks and disaster.
The third reason was the most important one. I had just filled the fountain (2,000 US gallons) and introduced the fish on Sept 1st. I got the fish from 3 different sources, and although they all looked OK when I received them, they naturally soon developed "Ich" as well as a parasitic copepod called Ergasilus (see "Parasitic Diseases" page). So I needed the warmer water for the treatments which I just finished before the cold spell hit. They all seemed at least temporarily cured.
During the extreme cold spell in Denver from the 18th to 25th of December 1998, when temperatures stayed about -19F for several days (according to the weather reporters), the top surface was solid 5-6" thick ice, except the surface stayed open behind the ice that formed a solid wall where you see the icicles in the above photo, and around the de-icer.
After the severe cold spell from the 18th to the 25th of December (weather forecasts said -19° Fahrenheit but my minimum-maximum thermometer said -6° F) there was a large amount of ice almost covering the surface, which in many places was 5 - 6" thick by the 23rd. Between the heaters, warmer temperatures and the sun the ice totally melted by the 27th.
I learned that icicles formed off the lower bowl whenever the temperature dropped below 15°F. They totally melted by about noon when the sun hit them.
You can see by clicking on the following charts the pond temperature was fluctuating between 45°F and 50°F for most of the winter except for the extreme 7 day cold spell. Although I did feed them occasionally I probably could have fed them for most of the winter.
Although many say food will rot in the Koi's stomach below 45°F and kill them, I have not seen any reliable sources quoting how long it takes for the food to rot, or more importantly how long it takes for the food to clear the stomach. As you can see from the charts the temperature sine-waved up and down on about a 4 day cycle with the heater.
The charts are showing me that wind-chill is very important. I also notice an increase in evaporation on windy days.
Click to enlarge the graphs then click on your browser's back arrow to return!
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