Introducing new fish?!

[Lilly T]

Hi! I have a 60gallon Goldfish tank with three yearling fancies! I just rescued two 7 year old fish. (A Moore and a stunted Comet) After quarantining the older fish, I’d like to move them into the 60 gallon with the others. Are older fish aggressive to younger goldfish or vice versa?

Edited November 18, 2020 by Lilly T

[Fonske]

How big are the yearlings and the old fishes? In my limited experience with goldfish I have not seen them being aggressive to each other as long as they are close enough in size so one is not trying to eat another. One old stunted comet I got went to a carp tank for a while and did some pestering of the carps although they were much bigger than it. These days the comet is with some fancies and everything is peaceful so far. 

[Andy's Fish Den]

I would say for the most part they will probably get along. The comet you might want to watch at feeding time as the fancy goldfish will be slower to get the food and the comet may dominate the food. As a side note, I hope that you have some good filtration on that tank. I'm sure you have done research since you're quarantining the new fish, but goldfish make a massive amount of waste and their behavior of constantly digging in the substrate will dirty up a tank quickly.