Why is my critter feeder producing germs?

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Air pollution bubbles keep coming up from my critter feeder.
I've tried deconstructing the tile underneath in case something trapped in there was producing pollution, nothing.
I've tried making a screenshot but cannot find where the file has been stored.
This has been made as a preparation for my ranching room and is not in use yet.
I don't have a rancher or any critters yet.
What could be causing this?
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Gross or Brilliant? Using Bugs to Feed the Animals We Eat | National Geographic
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Images: Ron Lach, Karolina Grabowska, Ono Kosuki, Ono Kosuki