Whats on my fish?

Jun 24, 2005
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Alexandria, Virginia
#1
For the last month I've owned my two ocellaris clowns with little problems, but now there is a weird growth on the gills of one of them. It doesn't seem to be bothering my fish, but seeing it worries me. It looks kind of cottony and isn't growing at all. He doesn't seem to be rubbing up against anything to try and rub it off, and he acts completely normal. I've included a photo of the side in question.
I haven't been able to find anything on it, at least from what I've looked at in my books (Saltwater Aquariums for Dummies and Clownfishes by Joyce Wilkinson) and on the internet.
Any ideas?