As to the mirror carp thing, its hard to say, but this link may be of some interest in indentifying some of the more unusual even just common species of freshwater coldwater species of fish that can somtimes be found in ponds;
http/www.whom.co.uk/squelch/freshwater_fish.htm
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The reason why the pond water is so muddy is because of the soil washing off the banks surrounding the pond/lake, can you get any full pond pics? You should cut down on the soil banking surrounding the pond and use some sort of border (like made out of planks, rocks or logs etc) to help prevent soil from running off the banks by rain into the pond. If you do this is should help clear up the water a lot and make it easier to see what types of fish you have in there
.Does the pond have any filtration?
Pond plants, in general, are evolved to thrive off very little nutrients in the water, and too much soil/clay or other forms of nutrients being washed into the pond can cause algae blooms or make normal pond plants turn into weeds because of their thriving growth- duckweed can also be an issue. Koi carp can also eat away at the sides of the pond in their search for worms and critters living in the mud- this can make the water muddy, or make the sides of the pond spread so it becomes shallower.
Planting pond plants in the banks of the pond, as well as above water plants on the banks, can help keep the banks together as their roots systems hold the soil and clay together, preventing soil erosion
. Lillies can block out sunlight, also helping prevent algae blooms or help treat them, they can also help prevent the spread of other nuisance plants while still looking gorgeous at the same time
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In the first photo's, you have a question mark over somthing that looks similar to a hollow stick, how long/wide is it roughly? I know of a critter that looks similar to that, but it stays very small u'see.