The issue I worry about is the water warming up and then dropping very quickly. The backyard pond dropped 6 degrees last night.
It is not even as cold as it is supposed to be.
Are changing temps a lot worse on the fish?
The front pond is essentially a wood box lined with rubber. It is half burried in the ground. That one is not as scary, just have to empty it down about a third and turn the two 300 watt heaters up. It doesn't keep it warm but it is at least 50 degrees.
SPRINGTIME??? WHERE ARE YOU??
LizB