Welcome to the forum. I would be concerned with O2 first, and water temp second. You don't want the winter water temp to go much below 2.5°C. Typically the water at the bottom of the pond during the winter will be around 3.9°C.
If you have a few inches of ice and a few inches of snow, the O2 levels will start dropping due to no sunlight penetrating into the water. Winter aeration with the bottom diffusers no deeper than 1/3 the total water depth and keeping an area or areas open that equal to 1/10th to 1/20th of the total pond area should be enough.
Hi Esshup
Thanks for the nice welcome, and the reply. The pond is 1-4 m deep. I use a diffuser in the deep end of the pond. It enough to keep an open hole in the ice. If I want to measure the temperature during the winter, does anyone have an ide how to do it? An automatic way to do it would be greate
