Black marks have appeared on goldfish. One has died, others have the marks!!

wrote in message
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Hi
This morning one of our goldfish was dead. Other than 2 black marks on
his head he seemed quite normal.
Our pond is a garden pond about 6 x 4 x 4. It contains about 40
goldfish and apart from cleaning and feeding the pond is left very
much alone.

Cleaning? You didn't say how many gallons your pond is but it sounds
overcrowded to me. You need to allow 15 to 20 gallons per goldfish and have
decent filtration/aeration. What is the PH and hardness of the water? What
are the ammonia, nitrite and nitrate readings?

The pond has been going for about 10 years with no serious
problems. The thing that worries me now is that 2 other fish have
black marks although they look quite healthy. I know I have seen
discoloration before on the fish so I'm not sure if the black marks
are related to the death of the fish.
Any help much appreciated.
Thanks.

--
KL....
Frugal ponding since 1995.
My Pond & Aquarium Pages:
http://tinyurl.com/9do58
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