Whenever you add a new cichlid to a tank where another cichlid has established territory, the new guy will be at the short end of the stick, unless it realizes its strength.
So if you moved the oscar ro the JD tank, this is a normal reaction by the JD, to defend its territory.
If at some point you move them both to a new larger tank at the same time, then because no territorial lines have been already been established, it may work.
If you put one in a significantly earlier time than the other, the same problem may occur.
All cichlids set up invisible (to humans) territorial lines, that are generally respected if they both can work out a territory in a new space, at the same time.
Need help, moved oscar to a 125 and he’s not eating and his fin looks to be deteriorating. I️ have left him alone for 2 days thinking he was acting weird cause of the new tank but notice the fin messed up. He’s now upside down heavily breathing. Help!!
