I moved house a year ago & inherited a large well established fish pond with 20 goldfish in it. The fish survived last winter but I am concerned for their welfare this year.
Many of the plants in the pond (water lily, marsh marigold & bulrushes) were extremely overgrown & spreading out of control with large mats of roots, so we did a big clear out recently & re-potted them into smaller, more manageable pots. I am now worried that the fish won't have enough shelter etc to keep them protected during the cold weather. Is there anything I can do to make sure they survive? Any help and advice would be very gratefully received.
I live in a rural area in Northamptonshire, UK. The pond is over 2ft deep in the centre of the large pond which connects to three smaller ponds via waterfalls.

Its the depth of water that is more important.. The deep water (18inches or deeper) shouldn't freeze, so as long as pond isn't overstocked they should all be ok again this winter, can you give us a rough idea of the sizes of the goldfish and the size of the pond?
You can float something like a football in the water which will allow you an easy way to keep an air hole if the surface does freeze you can more easily take out the ball and break ice from the hole rather than having to smash through it the hard way!
What's the temp of the water? And are they still eating normal food at the moment? if you haven't already either stopped feeding or been feeding wheat germ up til now, its time to think about sorting that out. Feeding them summer food when its cold can cause problems as their metabolism will slow down with the temperature, normal food left in their stomachs will not digest properly. Wheatgerm sticks should be fed as the water temp gets cooler, and when temp drops to a level they will hibernate at they shouldn't be fed until the water warms in the spring and their metabolism starts up again.

That's the best explanation of why not to feed the fish in winter I've heard. I'd always understood it had simply got uneaten rotting in the pond and causing harm.
Karl.

What about if they eat things like duckweed?
Is it the protein content - that's what I thought mattered?

Its processed food that causes the problem, if its warm enough for them to be active they will find enough food in the water, bits of vegetation, insects etc, but yep the pellets take more energy to digest especially the high protein ones, and these will rot in the stomach if undigested through a spell of really cold weather where the fish will just rest at the bottom until its warm enough to move again.