We built a nice cage for inside the house for:
A male/female pair of Java Finches
A male pair of Zebra Finches.
It's 4 long, 4 high, and 2 deep. So no more birds will be living in it. So far so good. The Javas seem busy with themselves and are not aggresive to the two male Zebra's and the two male Zebras who were previously housed in a 1 foot by 1 foot cage (sad I know

So like I said, things have been going well, especially since I thought I might get aggression or something.
So far the only "problem" I have and I am curious about is one of the male Zebras (Elton) has taken a liking to the female Java Finch. He sings to her and sometimes tries to sit with the pair. They pretty much ignore him unless he gets right up next to them, then they either go somewhere else or push him away. However there is no violence, and he isn't bugging her all day or anything. But he has a crush on her for sure.
Is this going to become MORE of a problem, or will he give up eventually since she obviously is not interested?