I lost a brunneus fairy wrasse to prazi resistant flukes a few months ago. It went through two rounds of prazi but was still scratching/flashing. Sent pics to humblefish who verified flukes. I was able to save the crescent fairy though that was in qt with it.
Yes. All I had was a small, black, cereal bowl. Worked well enough to see a bunch of tiny white dots. I sent him the pics and started lowering salinity that afternoon. Sadly, the brunneus didn't make it but I was able to save the crescent.
So I’ve observed her a fair amount over the past few days. It seems like she only does this behavior shortly after she picks at the rockwork and then filters out a bit of the sand through her gills. I’ve noticed the behavior once or twice since then and it’s always been associated with her sifting sand through the gills! Hopefully that’s all that causes her flashing.