I'm in Tasmania, about 7°c on average in winter.
and I've no idea how I done it, their tank had a heater but it was only really in there to stop the tank dropping below 15°c.. I went to bed one night, got up and they had eggs in a rock cave (I never noticed the eggs before bed, but they could have been there then), I never thought anything of it, thinking that it'd be to cold for the eggs to hatch, but a few days later there were probably 150 wrigglers in the tank. I was shocked, even more so when roughly two weeks later the power went out for a day or so, and I only lost 6 or 7 fry.. Ever since I've been amazed at the resilience of these little fish, and their willingness to breed.. One day (when I'm a bit older) I would like to try it again to see if I can work out what it was that drove them to spawn the first time, and what the chances are of it happening at such cold temperatures.. Because I'd assume they're not too high..