If the fish seems to be healthy I would not do anything beyond a formalin bath and possibly lowering the salinity to 1.016 as a stress relief.
Most important with Regal Angels is to keep them eating, even if it's just a little bit every day.
Clams on the shell and Ulva or hair algae are good starter foods. Brine shrimp also worked for me.
I have currently 5 Regal Angels and all are eating like pigs. Some of them actually prefer flakes and pellets over frozen foods. All also consume some green hair algae. If your tank doesn't have algae you might want to feed some nori.
BTW, if you suspect flukes I would go to therapeutic hyposalinity at 1.010 to 1.009. This will in most cases kill the flukes and make it easier for the fish to breathe. This procedure is especially recommend with fish that already display labored breathing as they would have little chance to survive the oxygen reduction PraziPro causes. After the fish breathe more normally you could do a round of PraziPro for good measure.
Doing TTM with new Regals right away is just a bad idea as it is really just a preventative measure against Cryptocaryon, the least concerning of all possible parasites your fish might have. I have had Regals with Cryptocaryon and it took almost a month to get to a critical level and it never really impaired their appetite. I treated all of those with hyposalinity and it worked every time.
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