For those who have fish for pets, how do you get emotionally attached to them?

I used to have a female betta and she was pretty animated and cool. Being that it's a caged animal, it's not the same as a cat or a dog, since they can't seek out affection from you, but I got a certain joy out of trying to make her happy and healthy. She'd hop out of the water and take food from my finger (that's how they hunt in the wild anyway), and flared at my roommates and people she didn't recognize. And do a little dance when I came in my room.