Bio-modifier Lifeform change

    If i start as Kaelesh and build a bio modifier to gain planet fields, then switch to a different lifeform, what happens to my planet fields? Do I retain the extra fields on my planet for rock-bois?

    It's the exact same as the General +moon fields. If you have say, 250 fields base and get +30 fields from the bio modifier building, and then build to 270 fields, then swap to Rock'tal, you'll see that your planet has 270/250 fields. You won't be able to make more buildings until you swap back to Kaelesh. But you will keep your buildings that you already made.