How does it work? If I send up space science, will it turn to fish on my platform? Does that mean that nay space science gathered on Nauvis isn't movable to other planets?

its base game only. space age is marked as a conflicting mod. i dont actually know how sending things up works in space age cause i havent played it yet

in base game you just get the fish in your cargo bay like you get space science from satellites

Space Age has a new vanilla way to automate fish production anyway, which makes this mod less necessary for Space Age games (a Biochamber on Nauvis can craft 2 fish + 100 nutrients + 100 water into 3 fish with reset freshness).