Help quarantine Threadfin Cardinals

[martin.a]

The Copper Treatment done. All 6 Cardinals seem to be in an excellent condition. Time to start Praziquantel treatment. Fingers crossed for the fish. They look awesome. I really do not want to screw it up.

Is anybody aware of Threadfin Cardinals poorly responding to Praziquantel?

Can I please ask to review my plan:
Tomorrow (Sat. 24 Oct.) I will start lowering copper below 1ppm. Current level is 2.3ppm (chelated). I am planning to replace 60% of the water tomorrow to get it down to a hair below 1ppm. Next day, on Sun. I will do another 50% water change to get it down to 0.5ppm. Water salinity and temp. adjusted.

Can I start Praziquantel treatment with chelated copper at 0.5ppm? I will use PraziPro, dosage as per label 2.5 mg/L meaning 5ml per 20G/75L. My tank is 80L, so I will use 5.3ml.

Dosage is to be 8 days apart as per @Jay Hemdal instructions (PraziPro label calls for 7 days apart, but I assume this is to simplify the treatment schedule)

1. Dose #1: Sun. 25 Oct. followed by 30% water change on Tue. 27 Oct.
2. Dose #2: Mon. 2 Nov. followed by 30% water change on Wed. 4 Nov.
3. Dose #3: Tue. 10 Nov. followed by 30% water change on Thu. 12 Nov.

Are the water changes actually necessary? They will be stressful to the fish.