I live in Southern California, about 30 miles East of Downtown Los Angeles. This sounds like a really nutty question, considering I dont get snow or big ice in my yard or anything - but should I even look into heating my 600 gallon pond?

The air temperature will drop to near-freezing where I am, mainly due to wind chill... and I do get ALOT of wind every evening. I've only lived in my house a year, and im not sure what the high daytime temps are... lets just say 60 degrees.

Because the daytime and nighttime temperatures vary so much - Im sure the water will get pretty cool. I dont want to bring my fish (g/fish and 2 plecos) or plants inside because we can get unseasonably warm weather for weeks at a time too.

Im wondering if I can find some sort of heater that I can set for a specific water temp and if the heater never turns itself on all winter - then so be it, atleast I'll have it just in case. (I checked the heater link on Robyn's winterizing page and it no longer works).

What do you guys think?

If it were just the goldfish, you certainly wouldn't need a heater since they can live under ice. But the plecos don't do well under 50-55 degrees F at the least. A de-icer type heater will not kick in until it goes below 35 degrees F, too late for the pleco (and probably never that cold there anyway). A 600 gallon pond is a bit too large for large aquarium heaters but you could try that. It's possible the plecos may find it warm enough to overwinter without any heat. If you're unsure, you can bring just the plecos in for the coldest few months of the year (when the thermometer goes below say 55-60 degrees F). Ideal pleco temperatures are 65-75 degrees F. They get lethargic below that. As for that aquatill link, I guess they've gone out of business or changed URL's. Good luck!