Why is my oranda goldfish chasing my other goldfish?

I recently upgraded my tank from and 10 gallon to 45 gallon. I finally got the tank set up and moved my black moor in to the tank. I then decided to get two more goldfish. I just got them today, a oranda goldfish and a different whitch I don't really remember the type though. The oranda didn't have any aggression tords the other fish I got. But when I put them in to the tank he went around the tank for a wile but then started chasing the other fish. I have read that it could be 3 things, aggression for territory, playing, or matting. I also read it could lead to DEATH. I'm worried for my black moor whitch is very important to me, and also the other goldfish I got. I would like to know how to stoping the oranda befor any of them get hurt or even die?
Asked Jan 03, 2016
Technically speaking, it is not advised to house different types of goldfish together, so if I were you and valued the black moor that much, I would move the moor back to the 10 gallon, and leave the other 2 fish in the 45 gallon tank.
Answered Feb 03, 2016
Great job on upgrading ur tank! Forty five gallons is only big enough for two full grown goldfish though! I reccomend twenty gallon per goldfish, Petsmart has thirty dollar twenty gallons, move a black moor into a twenty not back into a ten!
Answered Feb 21, 2016

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