No suitable planet for migration?

[matthobbit]

I'm trying to get other aliens to migrate to my empire, but when I look at their opinion modifier it says that there is "no suitable planet" for them to migrate to, and they don't seem to have migration restrictions. I've specifically colonized worlds with droids that are perfect matches for the alien species (colonized it right before they did). Am I missing some special mechanic that prevents aliens from migrating?

 

[I_am_Nemo]

They also have to have worlds that are suitable for /your/ pops to migrate to. So unless they get pops with your hydrosphere preference, or colonize a gaia world, having robo planets won't do you any good.

 

[matthobbit]

That sucks! I just want to build a multi-alien Xenophile empire and this stupid arbitrary mechanic is preventing me from doing it.

 

[I_am_Nemo]

That sucks! I just want to build a multi-alien Xenophile empire and this stupid arbitrary mechanic is preventing me from doing it.

Eh, would you sign a migration treaty that resulted in pops leaving your planets, and no pops migrating in?