Hi everyone.
I wonder if any one can help help me.

I have a fairly large pond in my garden with a re circulating water fall in
it.
We have a large amount of fish (about 150) of mainly Goldfish (large and
small) and a couple of ghost koi carp.
Over the past few weeks we have had about 20 die and we are starting to get
worried.
I'm try to clear the pond on a regular basis but I am far from being an
expert.
I've just studied some of the fish and seen that some of the fish have black
spots on them (more of a cluster than of defined spots).
Does anyone have any ideas or some advice.

I intend to clear the pond on Saturday to try and clean it out.

thanks in anticipation.

regards lee