Aquarium heater in a seedling tank
Rich Sacher Photo

Pond Heating Possibilities

by Jeremy Prentice
Royal Botanic Gardens Melbourne

For those of us who are in the position of having to heat our ponds to grow the aquatics we so love and enjoy, one of the challenges to overcome is controlling the water temperature. I asked this question of members of the Victoria Adventure mailing list and have collated the responses given and paraphrased summaries below.

The more straightforward options:

(i) The most obvious is the aquarium heater. These units are (usually) perfect, and are useful up to a certain size pond, before getting extremely expensive -- I have it on good authority though that the decision to invest in them for a large pond is a very good one…

(ii) Another closely related method is the use of spa or hot-tub heaters. Apparently these can work by circulating the water through a heated area and returning to the pond. One member heated their whole 50ft glasshouse using this method (I assume the heat radiated off the water body…)

(iii) A hybrid of passive solar heating and electricity: pumping (the electrical bit) water through a pipe system that is exposed to the sun's warming rays. This is most useful where you get a lot of reliable sunshine, and may be difficult to control the temperature;

a. One list member said that he was going to trial a setup similar to this where the pond water would be cycled through a separate heating tank, which in turn was heated by hot water pipes warmed by a solar panel and topped up by an electric boiler if needed.

b. Yet another method mentioned was to pump the water through a crock pot: Apparently it was much cheaper than using aquarium heaters!!

Other ideas:

(i) Running a pipe system through the pond, and connecting it to an existing glasshouse hot water heating system (obviously only practical if you have a heated glasshouse!) These are usually controlled by thermostat, so the temperature can be monitored.

(ii) Using solar panels to generate electricity for a heating element - I don't know of any unit doing this already, but surely there is something out there…?

(iii) Covering your pond with plastic to help keep the heat in, or build a straw bale pond and cover with a storm door!

(iv) A product such as the Thermoplanter would probably be extremely useful too, perhaps eliminating the need to heat the whole body of water. I'm planning to trial this product later this year 2007 (hopefully growing Victoria outside in Melbourne, Australia, for a longer season).

All thoughts, suggestions and corrections are invited and welcome. Ideas that balance outlay and ongoing costs with practicality and simplicity always rank highly on the list! (Email sent to will be forwarded to the author.)

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