Temperature dropping rapidly (from 70 deg to 20) in a few days

[cokewithvanilla]

I am trying to figure out what to do. I have a pond that is only 2.5 foot deep (came with the house) 750 gallons, houses 2 koi and 4 goldfish. . I finally got everything sorted with the filtration to keep with with the fish waste and keep the pond clear. I did not expect the weather to change this quickly and I am trying to figure out what to do. Right now, due to the monday holiday, everything is delayed until tuesday for arrival. Anything i order may be too late. A 1000 watt heater will take over a day to heat the water 10 degrees... that's about as much as I am going to get on a 12v 20 amp circuit . I cannot find any pool/pond cover locally to keep in the temp. Is there a DIY solution I am missing?? I'm thinking water heater elements in some kind of inline container... only id have to get 240 out there.

I am worried that the temperature swing could kill them, mainly due to that happening to one of the fish last year shortly after i moved in. Any help would be appreciated.

[graybird]

If there is a pet store nearby, you may be able to find multiple 250w aquarium heaters. I have used them to heat my 400 gal quarantine tank. You can also partially cover the pond with a 4x8 sheet of rigid insulation, which Home Depot carries. Even if you only cover it at night, and open it up during the day to let in the warmth of the sun, that's something.

That being said, since the temp has already dropped, I'm not sure you can put the horse back in the barn.

[cokewithvanilla]

i found a 1500 watt 120v heating element, but I think that diy project can wait. They have 5 300 watt heaters in stock between all my local petsmarts. I am going to pick them all up now and install. Hopefully i will beat this large temp change, as it is 50 degrees right now .

thank you!

[koi4u2c]

I have had those same temperature drops. Even had culled goldfish living in above ground 800 gallon stock tank, appear to freeze totally, but never lost any of the fish.

I would just cover your pond with 6ml plastic. I get mine at an agriculture supply store. It can also be found at Home Depot, or Lowes.
I would raise it above water level. If in the sun it will heat the water in the day time and possibly keep it from freezing.

[mplskoi]

Covering ponds and insulating them is often much more effective than trying to heat them. Blue solar cover from a pool or just 6ml plastic covering out and beyond several feet past the perimeter of your pond is best. Depending on your situation you might want to lay some long boards across the pond so the plastic cover is just above the water surface.Or if your pond can handle two or three inch thick sheets of foam that works well. Especially if your pond has a flat top perimeter.
I am in Minnesota and my pond is at 62.4 today with no heat source. Just good insulation.

[RichToyBox]

A simple lean-to type structure with the 6 mil poly sheeting found at Lowes or Home Depot will help immensely. Cooling is caused partially by radiation into the atmosphere, but mostly be evaporation (think jumping out of a shower in front of a fan) and evaporation is increased with wind velocity (carrying the higher humidity air away from the surface of the pond) and by warm pond with cold air (think steam coming off coffee cup), so a cover will keep the high humidity air from blowing away, and keep the cold air away from the surface of the pond. If that and any solar gain during the daylight hours doesn't keep the pond above 50 degrees, then heaters can be used but the cost of running heaters is not insignificant. I had two 1500 watt heaters going on each of my ponds and that translates to 3KWH for each hour of the month, or about 2200 KWH per month times the rate for your electricity. For me, it more than doubled my electric bill for my all electric home.