I‘ve been looking for a Yellow Pyramid Butterflyfish, for some time. Found one at a LFS, that was eating Flake. Quarantined it in a 30 gallon and observed, notice a place on its fin near the gill. Started slowly ramping up the Copper Power, died before I got up to the Therapy Dose. One of the weird things was it would only eat Flake Food, wouldn’t touch Angel/Butterflyfish formula, or the S F Bay, Combo Pack. Could this be Cyanide Poisoning? BTW, the tank is established with Foam Bio-Filters, and had zero Ammonia, that was checked twice a day.