Hello there.

4 months ago we bought 2 Red and White Ryukins for my 3 years old daughter.  They used to be in a 30 gallon tank. After only a week 1 of the Ryukin died.  So the other surviving Ryukin was alone for a while.  And then my parents came by to visit us and saw that the aquarium only have one Ryukin and my daughter was asking for a new goldfish.  So they went to the pet shop and when they came home they brought not only 1 but 2 pearlized fantails and a new 55 gallon fish tank.  So we set up the new tank immediately since placing 2 other fantail in a 30 gallon tank might not be ideal for them.  So we transferred all the fishes in their new home.  They had been getting along and seems to be healthy for the past 3 mos now.  Last week my husband came home with another Ryukin so that the goldfish would be in pairs.   He didn't realize that the one he bought was much much bigger than the existing Ryukin. And true enough after letting him float 30 mins with the plastic bag on the tank for it to adapt it was time for him to be released and join the rest of them.  I immediately noticed something odd about this Ryukin because it started chasing all the other 3 fishes around!!!   I got worried so I demanded it to be moved to the old 30 gallon tank until we figure out if he's really actually hurting the other gold fishes.
So I want to ask if we place him back in the bigger tank to join the rest of the fishes would he eventually adapt and stop chasing the others around or would it be better to just leave him in the 30 gallon tank just to be safe?  It's very pretty though we really want him to join the rest..

Thanks in advance

Jen.

Did you quarrantine that new fish? Its always good to keep new fish separate for a while, in case they carry diseases. This way, all your fish stay healthy adn you dont have to worry about sudden deaths