I'm over in the UK and it's currently winter. Weather is still rain and cold. The odd rare day it can get to 10C. I feed wheatgerm when it gets to 9/10C. Filter and pump is still running. Clean filter once a month. Pond needs a clean. Its netted but some leaves have still got in. I have 3 shubunkins, one comet and one goldfish from a tank inside my mum and dad's. It's the first winter the large goldfish has had to endure in the cold. The only way I can describe it is it looks dirty. Like it needs a wipe. Their is muck on the liner and at the bottom and on roots of plants. They hide under a sedge plant I have in a pot which is balanced on a shelf and half over the deep part. I've took the best pictures I can. I'm worried it's a disease/fluke. Would flukes survive at such cool temperatures? Should I catch the fish over the weekend and see if the stuff wipes off?