"Carl Beyer" wrote in message
...
I don't know if this is a problem or not...

I have a rather large catfish (I swear he was 1.5 inches when I got him)
now he is a good 16 to 20" (same as my large koi).

We are in LA area.

His whole back has turned grey, and rather suddenly. Do they shed? Do
they age? Did he sunburn?

I am getting the water tested today, but everyone appears in good
health, including the catfish... no rubbing or anything like that. No
one else has any spots...

And it does not look like spots. THe whole back is just grey but his
darker colors are still strong along the sides...

Carl

Can you post a link to a photograph of the area in question on the fish?
What kind of catfish is it? what are your water parameters?