Simply Koi and More Koi

Hi,
Wonder if any of you would share your thoughts on the following:

If a pool is heated (13-14 degrees) and covered throughout winter,then do you try and cut down on heat loss through convection by cutting down on excessive water flow or perhaps even air flow?
I have two returns in a 7 foot deep pond, one from the main bio filter fed from the BD and the other from the skimmer. The skimmer only feeds a multi-vortex which is there to try and cut down on fines. Main filtration is plenty adequate! The returns are side by side, horizontal and about 2'6" down. An aerated BD is pumping a healthy 70 litres.
So........ In order to cut down on heat loss should I consider shuting off the skimmer during winter? Or the air? Or both? Or neither? Would it be an option to put the air and skimmer on a timer so that they only operates during the day, leaving the water as still as possible during the coldest hours?
Obviously I will continue feeding throughout winter, albeit on a reduced level.
And should I be taking the cover off once a week or so to check that all is well? (I guess the answer to that is pretty obvious!!)
Open to any suggestions. This is the first winter when my pond has been heated so it's new territory for me! (Dreading the leccy bill!)
Many Thanks,
Louie

Louie, the simple answer is no leave the air running, leave the skimmer running .... but if you must then the skimmer is probably the sacrificial item.... or lower the temp to between 10-12, as some heat is probably better than no heat. Cover the pond, but don't seal it in .... 90% of the oxygen exchange takes place at the surface and not in the column of air pumping up from your bottom drain. The air from the bottom drain serves the main purpose of setting up a current in you pond to ensure 1. debris goes to the drain and 2, there is good mixing of the water and no dead/stagnant spots.

"Cover the pond, but don't seal it in" ... the bad air that will eventually gather in a sealed in pond, needs to be let out, block the draft but allow exits. Don't worry the air between the pond surface and the cover will form a thermal barrier and reduce the heat losses. I've tested this in the past, my pond been at 10°C, the air under the cover has been at 10°C and the air above the double glazed sheet has been at -1°C.... and my heater was cycling on and off.

Just remember, irrespective of what you do heating does cost, so if you are going to cover your pond - heat to the minimum as large healthy fish don't need as much - some say none at all

Good Luck ... I'm off to "work" for my heating