[Delphinus]

That's interesting about the flatworms not being affected. When I did praziquantel I bought both Prazipro and Praztastic but only used the Praztastic, which is I think more concentrated so it could be that it takes longer with Prazipro. I did not have the red flatworms or the smaller clear ones, or at least, none that I knew of, but I did notice weird flat worm looking things coming out of the rock and floating off into the current, so I figured it did have an effect.

I intended on doing a second treatment because the tang was so badly "infected" but after about a week I did start to notice improvements .. so elected to hold off on the second treatment and only do so if really necessary - but it never proved to be necessary.

I had major amounts of green slime algae form on the glass shortly after treatment that lasted until well after the treatment stopped so I was all too happy not to do that second treatment.

So my advice is to keep watching for now, it might take a few more days. Hopefully that's all it is. Good luck!