So I colonized a planet full of mushrooms

[Mr.Poopybutthole]

My ethics dont allow me to either enslave or kill them off, what do I do?

[MACIORELLA]

Eat them and enjoy the ride.

[Aieonae]

and get psychedelic

[Riftwalker]

need to uplift them. :P

[Vim]

By the internal logic of the game, you can only "colonize" an already occupied planet if it's full of pre-sentients. In which case what you do is get the technology "Uplift" and you can re-design them into an extremely useful pop for your empire with your choice of planet type and traits and a limited choice of their ethics.

[drake_hound]

uplift them and fix there genes to be more compatible with your game.

[Mr.Poopybutthole]

ah ok thanks!