Holy Atmospheres, Batman!!! aka stating the obvious

[Stone Mill]

This is what we call a "No-Duh" in NJ... otherwise known as a "DOH!"

Colony ships load different population types, not necessarily from the planet that built them. You have to think of population as cargo. If you have several planets, each with different atmosphere breathing populations, you can use the "Load Cargo" order to pick up the right type for the intended destination on its way.

Sounds pretty obvious, huh?

I remember banging my head against the wall, trying to remember why my new Carbon Dioxide Giant only gave me 5 facilities. My race's breathing type was Carbon Dioxide... there was a green asterisk next to the planet... what gives? Then I remembered the colony ship was built at a planet I had received from an ally (breathing type: oxygen).

Then someone told me about right clicking the population icons in the planet display window.

I take all this for granted now, but it was a bit confusing as a newbie!