A Grobo's intake fans do not all turn on when you begin a grow. 


  • The fans are off during Germination (Stage 1) to prevent them from drying out your seedling.
  • The bottom fan will turn on during Early Vegetation (Stage 2).
  • Then, in Late Vegetation (Stage 3), both intake fans will be on for the remainder of the grow. 


Gen1: The intake fans are in the back wall of the unit.

Gen2: There is an internal fan that is moveable in the unit.


The crossflow fan, behind your carbon filter, should be running at all times to pull air out of your grow chamber, through the carbon filter, and out the back grate. 


Still have questions? Please see HERE for how to contact us.