What should I get my bf for his birthday?

It would be funny to get the ant farm but then get something he'd actually want too.

Why not get him one? And some other things. He may joke about it but there is some truth in a joke. He may have wanted one since he was a kid and never got one. If you get him some other things with it he will see that you have a light hearted side too.

well now you gotta commit to getting him an elaborate ant farm

If you can get him that, get it.

Why not :p ?

Get him an ant farm.if he doesn't like it he can release them into the wild.