Re: species or race?
I would say it would be species. Races are groups that are within one species. It is doubtful that all of the various aliens would be homo sapiens, or even one other species scattered around the galaxy. I'm sure the various types of aliens originating from different planets would have different DNA makeups. So I would say they should be species and not races.
But I agree with some that you could have different races within one alien species. So I guess I agree that you could use both.
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