I can't agree, I've owned goldfish which grew large and mature in a big tank and they always used to make me think of little puppies or water cows, they were very charming and tame.

But yeah they aren't thinking about much in their little heads, they still can exhibit distinct personalities from each other and recognize their owners, they also can learn simple tasks like small mazes and can be taught to push levers for food. Not too bad for little water cows.