I had a quick look through our pond stickies but we don't seem to have anything on winter prep. I've never kept a pond so I'm a little hazy on best practice for winter, however, there's a good post by koinut here which might give some tips
Marsh marigolds should be ok left where they are, as a native plant I'm sure they can cope with winter weather.. Should die back and go dormant until the spring anyway. Leave aeration on, could help prevent water surface freezing, and put something that will float on the surface so if it does freeze you can remove it so their is an air gap, you may need to break the ice but don't hit it as can shock the fish.
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The link suey2 listed pretty much says it all, but in summary.
Keep all filters running 24/7.
If pump fed you can raise pump off pond floor. (Couple of bricks work wonders)
Turn off / remove / by pass your UV (Ice can ruin it)
Turn off / remove any air pump / air stones. (Only used in summer)
Bubble wrap is good if mounted on a frame above the water. (keeps air in, cold out)
If you don't have bubble wrap, or you haven't done so already, put a net over the pond to stop the leaves from falling in. They will sit at the bottom and decompose.
Any decorative features (Fountains / water spouts) should be turned off.
The filter water return if its via a pipe can be lowered closer to the water.
If the water freezes, use boiling water to make a hole for gas exchange. Never hit the ice. (Remember old films with submarines and depth charges, well.........)
Feed the fish with love and care ONLY. Fish metabolism is determined by water temp. So as its cold the metabolism is very slow. If it gets warm for a few days, DON'T feed them. (other than love and kindness) they will eat the food but it will stay inside and rot.
Good quality costs. Bear this in mind before you start.
Sorry if my reply is NOT want you want to hear, but what I have said is true.