Trying to eat the black Moore? Has it been picked on by the fish? Have u witnessed it. If that’s the case then move it or get a divider. Would suggest post ur water parameters. Make sure the nitrates are less than 20ppm. Start some maracyn2. Check ur water daily.
No it’s never been picked on before the smaller gold fish just keep going for the eye for some reason. I don’t know the size of my tank I just know it’s huge, my other half does water changes often so the water is very clean.
Would suggest separating it so its not bothered. If u can put in another tank and dose some maracyn2 and keep the water cycled and clean (nitrates <20). If not able to place in a quarantine tank then suggest dosing the tank with maracyn2 and checking the water daily. Hope it recovers. Best of luck.