Cupramine killed my new quarantine fish! Anyone else experience this???


Has anyone experienced this???

I bought 2 small Azure Damsels, 2 Purple Firefish, and a small Aptasia Eating Filefish and put them in my simple quarantine for 24 hours. They looked well and were all eating. The next day I added the recommended half-dose of Seachem Cupramine, and they were looking fine an hour later. A few hour later I found a Firefish and an Azure Damsel dead, and the other fish looking half-dead!

I quickly transferred the "survivors" to my other quarantine tank with plain clean saltwater, and the Firefish improved, although the Damsel and Filefish are still looking quite unwell a few days later, with neither eating and the Damsel breathing hard and the Filefish just weakly drifting around, and I am worried they might be permanently injured...

I checked the temperature, salinity, ammonia and nitrate and all were fine, and this was newly mixed and aged saltwater they were in.

I did just treat my previous batch of clownfish, Banggai Cardinals, and Royal Gramma through the same quarantine, consisting of 14 days of a hybrid tank-transfer method, changing tanks twice a week, and being treated with the recommended dosage of Cupramine and General Cure (GC being Praziquantel and Metronidazole), and saw no signs of stress apart from the Banggai's being reluctant to eat frozen food.

I'm absolutely shocked and gutted as I've been trying to very carefully take every precaution, and I don't know what to do now and how I could/should continue any treatment on these remaining fish, (apart from raising copper levels much more slowly). The only different thing from the previous batch was that I had a new internal filter of a generic brand I bought online instead of a sponge filter, but I don't know if this could have anything to do with it.

(I appreciate this is a fairly aggressive quarantine procedure, but after researching this extensively and having had friend's tanks wiped out from adding a new fish, I had thought this was the best approach.

Can anyone kindly advise please??????
Oh man, that’s tough. I commend you for trying to do things the right way, and cupramine is a proven treatment. However, it can be particularly hard on fish to adjust, even with the mildest of medications. It’s not uncommon to kill fish when trying to cure or treat them. Next time, try increasing the dosage over a few days, as opposed to giving them the full dosage all at once. As with everything in this hobby, acclimation is highly important.
Copper is like chemotherapy. It’s poisonous to fish but more poisonous to invertebrates so you add just enough to kill the invertebrate paricites but not enough to kill the fish. Did you test your copper levels?
  • Like
Reactions: Mxx
I did test my copper levels with a Hanna Checker and it wasn't at the therapeutic dose yet even, and no I hadn't used any dechlorinators.

I spoke to the shop and did some further research. Seachem say Cupramine is a safer version of copper, but then one expert also said that is just marketing BS. And from many experienced sources I've now heard that Copper Power is the safer version, and that it is best to raise the levels very slowly, like over 5 days, rather than the 2 days recommended by Seachem, so I've purchased some Copper Power now to use instead.