From Galactic Fleets Wiki
The Bio Dome increase the amount of food created by your workers.
Bio Dome Bonuses Increase to Food Production.
Lvl 1 = +5.71428571428571%
Lvl 2 = +11.42857142857142%
Lvl 3 = +17.14285714285713%
Lvl 4 = +22.85714285714284%
Lvl 5 = +28.57142857142855%