Dipping weak fish can be an issue - in this case, you are dipping as a diagnostic tool, and the fish would be post quarantine, as healthy as they are going to be. I've given FW dips to literally thousands of fish, and yes, they will give you all sorts of stress signs, but only die if they are already moribund, or in some rare cases, if they are so heavily parasitized with flukes, that when the dip knocks the flukes off, the fish literally bleeds out.I’ve literally never had good results w a freshwater dip ever. Every fish I’ve ever dipped gets really stressed and I have to pull them out before the 5 min. I match the temp and ph in the dip so I don’t know what I’m doing wrong.
I’ve actually never had a fish make it though 2 doses of prazi and 2 weeks of copper and show signs of disease after.
The reason the prazi doesn't control Neobenedenia is that species of fluke is an egg layer and prazi doesn't affect the eggs. The eggs can take up to 30 days to hatch. Two prazi treatment will miss eggs. Four treatments, spaced 10 days apart also won't work - have you heard the term "prazi resistant fluke"? Well, it isn't the flukes that are resistant, what happens is that heterotrophic bacteria grow in aquariums previously treated with prazi, this bacteria consumes prazi as a food source. By the third and fourth treatment, the bacteria is eating the prazi faster than you can add it.
The best treatment for Neo is screen for it with FW dips, and then if seen, hold the fish at half salinity (16 ppt) for 35 days.
Neo is more or less of a concern depending on the species; pomacanthus angels, pyramid butterflies, lookdowns and some others almost always have it. I rarely see it in wrasses or clownfish.
Jay