Hi all,
I read this post a while ago and wanted to respond, but I lost track of which thread it was in
. They say the mind is the first thing to go
. I'll give a more thorough answer later. Maybe I'll do a write-up on it since it's such a common question. The short answer involves thiaminase enzymes, and the concentration of thiaminase enzymes in an organism determines their pathogenicity. There's a wide variety of effects that thiaminase exposure can produce, ranging from diminished growth to sterility and even death. Individual variation and concentration play a role in determining why one organism may succomb while another (eating the same diet) appears healthy.
The scales aren't toxic, and the pigments that cause goldfish to be orange are called carotenoids. Some people actually supplement their pet's diet with carotenoids, xanthanoids, porphyrins, and flavinoids to bring out more vivid coloration. They're not toxic unless they reach impractically high levels. I'll write more later,
Rick