you can measure RH with a hygrometer, but you might want to get a humidistat if you plan to grow long term. The hygrometer just takes a reading, the humidistat takes a reading and will control fans, dehumidifiers etc. to control RH.

If you are in a grow bow you will only need one fan, just make sure there is a passive intake to allow for good airflow.
GanjaRobPDX Reviewed by GanjaRobPDX on . First time Grow Box Lesson So my grow box worked really well I think, the high reflectivity gave the plants lots of light even though it's an all T5 setup. But I did have the Powdery Mold problem. Two things I did, over watering so water ran out of the bottom of pots and wet the wood and made it really humid in there, and fans only on during light. I'm thinking that's the lesson. So after I clean out the box with bleach and start a new grow I'll have the fan go all the time, maybe setup two fans, intake and Rating: 5