OK here's the deal with internal parasites/intestinal worms. Praziquantel (i.e. Prazipro) eradicates
most strains. However, there are a few which are prazi resistant and for these you must use metronidazole (exs. Metro-MS, Seachem Metroplex). IME; metronidazole is actually superior when it comes to treating intestinal worms because it covers more strains, but you still have to use prazi to kill gill flukes.
So what I've started doing in QT is treating with "API General Cure", which is a prazi/metro mix, instead of using Prazipro. And being API General Cure is in
powder form there is less chance of interaction issues if you have to mix it with another med (like copper) than there is when mixing with
liquid Prazipro. Prazipro contains Oxybispropanol, a solubilizing agent, and mixing this with certain other meds can lead to a bacterial bloom which can starve all oxygen out of the water.