Koi Pond Left Unmaintained

Question
We just moved into a home that has a good size koi pond.  The water is so murky that, at first, I didn't believe that any fish could be living in it.  I was mistaken.  I began draining it because there is about 1/2 a foot of sludge on the botttom that I had planned to shovel out.  As I was doing this I found many (maybe 15 or 20) very healthy looking fish.  Some of them are about 8"-10".  I stopped draining.  Now I dont know what to do.  There isn't even a filter or water feature.  I'm shocked that there are so many and they have been able to survive.  How can I clean the pond without killing the fish?  Do the vacuums work for this kind of thing?  Should I just leave the sludge and leaves at the bottom and get a functional filter?  What kind of filter?  Help!  Thanks,Taryan

Answer
Hello Taryan
Wow, this is a bit of a complicated subject to handle here in its entirety, but I will try to give you some brief pointers to get you a start.
Yes, the sludge should come out.
Your best bet is to take a large container (a child's splashing pool works well), fill it with water from the pond. Add a pond pump to move the water to keep oxygen levels high and then move all the fish into it (be sure it is in the shade).
That will leave the pond empty to get the sludge out.
After cleaning the pond (make sure not to use any chemicals of any sort), fill it back up and add de-chlorinator. Adjust pH, install the pump and now take some of the new pond water and gradually add it to the splashing pool until the water temperature is even in both the pond and the pool.
At that point you can move the fish back to the pond.
You will need to install some sort of filter to keep the water in the pond healthy. Pumps and filters should run 24/7.