Hi Georgi,
The advice people give in fish shops is notorious for being wrong in most
cases unless you are really lucky! Black marks are unlikely to be natural
pigment changes. Colour changes are common in fish but usually they turn
lighter not darker if this happens.
What readings did you get on your tests?
Ammonia should be at 0, nitrites at 0 and nitrates under 20. If higher then
they will cause distress and burns to your fish. Sometimes on the test kit
instructions they do say that amounts higher than these are in safe ranges
but it really is best and healthier for your fish if you keep them at the
levels I stated above.
Mel.

"Georgi Kirkwood" wrote in message
...
Thanks Gunther

I will do that.


"Gunther" wrote in message
t...
In article ,
says...
Hi, I am the girlfriend!

I have done the 30% water change earlier as suggested - thank you Mel.

I went to the fish shop and explained the problem and advice I got
from
this
newsgroup. The bloke in there has always given me good advice in the
past,
he said there was nothing wrong with the fish, it was a pigment
change,
and
that this does happen to goldfish over the years. He said what I
should
worry about was if the spots were white or red.

I did the test for the water as suggested too, and there is no problem
with
ammonia and nitrites or nitrates - all levels are fine and within the
ok
ranges on the test kit literature. I called the guy in the fish shop
to
make
sure I was reading the results right.

He said if it was ammonia then both the fish would have the problem
with
these burns.

So my question is, what do I do now!?!


You keep doing the water changes as suggested and
monitor ammonia/nitrites/nitrates closely.
It's simple enough to do, and is never harmful
unless you do it wrong.
G