Here's how I determine when to water. When the container your plant is in feels very light it is time to water. The frequency in how often you water depends on tempature, airflow and humidity. Try to keep the tempature between 75ºF and 85ºF and the humidity no lower than 40%. Also if you have your fan blowing directly onto the growing medium it will just dry out faster. My last grow I had to water almost three times a day. Hope this helps chris. :thumbsup: