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phototoxicity of malachite green

Hi all,
  This reminds me of a bit of info that I came across a while ago,  a
blue dye is now being used to control a particularly anouying wasp whose
larva parasitize fruit (especialy papaya).  This dye (I want to say
methylene blue but that may be inacurate) is only effective if the wasp
consumes the dye and then is exposed to direct sunlight.  Now I am by no
means a bioligist, but I expect that an insects exoskeleton must be at
least as good at blocking light as fish scales if not better.  If this
is true then would it not be possible for fish to feel the effects, 
especialy fry, weakened, or very sensitve spiecies?   Now I realize that
malachite green is used everyday without real problems, and that
although we as hobbyists try hard to mimic the sun in spectrum and
output, most of us probably don't even come close ;).  So, while this is
probably more academic than practical, I think it is still interesting. 
Any takers out there ?


> Old stuff, new uses - Malachite green is one of the dyes used in
> photodynamic therapy, a relatively new cancer treatment.  These
> dyes have the property of forming highly active (toxic) derivatives
> when exposed to light.
> [....]
> I've wondered whether it works by the same mechanism in the aquarium,
> and whether the fish scales are protective from light, [....]