I tried using chloroquine phosphate to quarantine 100 juvenile Red Emperor Snapper (Lutjanus erythopterus). On the first day, I added 15 ppm. Since the drug degrades over time, I then added 2 ppm every other day, for a total of three supplementary doses. Before the third top‑up, the animals were doing very well and feeding vigorously. However, after the third addition, acute mass mortality began to occur. At the same time, water quality started to deteriorate, with ammonia‑nitrogen rising to 0.25–0.30 ppm. I put a small amount of activated carbon into the tank to adsorb the drug, and then added six porcupinefish, one moorish idol, and one clownfish to the system. The next day, five of the porcupinefish died, while the moorish idol appeared unaffected. Water quality did not improve, and I suspect that both the juvenile snappers and the porcupinefish do not tolerate high concentrations of chloroquine phosphate well.
