optimum number of plants per 4 bulb 4ft t5 fixture

[oldfogey8]

The room my tent is located in is quite small. I don't exhaust the air outside of the room. I am sure that is my problem. I don't anticipate it being a problem this grow though as I should be done by mid May at the latest. The ambient temps in the basement grow room should help keep it cooler. I hope...