Almost forgot - you can also capture one of the enemy's colony ships and set up a new colony on a world with the appropriate atmosphere... or, if you want the tech, just transfer the new slaves (I mean immigrants ) to an appropriate existing colony and then analyze the colony ship to get the colonizing tech.
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L++ Se+++ GdY $++ Fr C+++ Csc Sf Ai AuO M+ MpTM S Ss RRSHP+ Pw- Fq->Fq+ Nd+++ Rp G++ Mm++ Bb---