I have been lifting the covers during the day, and replacing them for the night. In fact mine will stay on until the night time temps stabilise most likely end of April.
The koi have become more active over the last few weeks, I think it is down to the lengthing daylight more the rise in temps.
When the temp hits 12-13degC it is worth getting the microscope out and giving the Koi the once over after the Winter, at least at this temp you can treat them if you discover parasites.
I also will have some Koi to move on during this Summer, not too sure which ones yet?
Nothing planned for the pond.
Dave.