What heater would you recommend for a 170 gal pond?

[saberry]

A friend of mine is starting a pond and was asking about heaters. I didn't know if he should use regular submersible aquarium heaters or if there are heaters made specifically for ponds - but I did know where to come for the answers! Can anyone help me point him in the right direction?

[AngelFishFan]

Definetly not an aquarium heater.. they will crack, because they are GLASS. Ever see a glass pane heated and then rapidly cooled? SHATTTTTER. You want to purchase a regular pond heater.. .there are many out there. As long as they float, and as long as they are warmer than 32 degrees farenheit, then it'll work. The only thing you have to do is make sure that there is a hole in the ice. This allows the [acronym:6939abb017="Carbon dioxide"]CO2[/acronym:6939abb017] to exchange for Oxygen, thus allowing the fish to breath "fresh" air.

[saberry]

Aquarium heaters aren't all made of glass and the better one's are of pyrex type glass. Bare in mind this is just south of Houston so freezing isn't the main issue as it rarely happens. He's more concerned with providing a stable environment for the fish. As I understand it, the dangerous temp zone is between 50-68 degrees F. That range describes the weather here for a good portion of Fall and Winter. He's looking to maintain a temp above 70 degrees.

Does anyone have a link to any specific heaters you would recommend for this task? What do you other Southerners use?

[boroughmal]

In Ireland the ponds rarely freeze but the optimum temperature above & below 50 degrees faranheit is the diffrence between the fish moving about or going to the bottom & staying there.
The optimum over 50 degre period is only 4-5months of the year.
In order to keep the temperature up I have 2 sheets of bubblewrap which go onto the pond either side of the summer. This keeps the fish moving and up above the optimum,
Later in the year I have a coil of 100metres of polypipe fixed in circles around six uprights and connected to the house boiler. this gets turned on for a month or so, when I let the winter do its damdest.
This gives me a season of 8-9 months in a 4-5month climate & my fish grow rapidly (10" per year)
Would a simular system work for you or do you have bigger summers/