Have you considered salt, pimafix, or praziquantel?
Copper treating like you are could work, as it will kill almost any invertebrate, However, they may have an exterior that shields them from copper. If that's the case then they probably just get oxygen through the host bichir instead of the water, preventing them from coming into contact with the copper. I dunno, I've never had them personally. Careful with the copper though. It's rougher on fish in a freshwater environment than in a saltwater environment. Luckily bichirs and cichlids are tough.
I have never tried a hydrogen peroxide bath to get rid of these but it might work. A saltwater dip might work too.
any meds that has praziquantel will cure it, the brand is not important whats in it is what matters.
last time i got this i used "API General Cure", just check the ingredient of any external parasite med you can find for "praziquantel".
the dosage is 75mg praziquantel for every 10gals, its safe for all fish.
when dealing with parasite, its better to familiarize with the active ingredients involved to cure it and not particular brand names, and you will find they contain the same basic ingredients for the same parasites or class of parasites.