ABOUT: The MH light (metal halide)is a bright white light that gives off lots of blue spectrum which is perfect for the growth cycle. I run this light 18 hours a day, when its time to turn your plants to flower you use a HPS light (High Pressure Sodium) this is the light you see in the video, it gives off a yellow light that has lots of the red spectrum which is perfect for the flowering cycle. The HPS light is run for 12 hours a day. The reduced light period together with the red spectrum triggers the plants to begin flowering. This is what happens naturaly in an outdoor situation, the only difference is you have controll of when each fase takes place. My whole system is automated, the only thing I need to check is that there is enough water in the sump to fill the pots. Every 2 weeks I run fresh water the system for 5 days to prevent salts from building up. When its time to harvest I run fresh water through the system for 10 days to remove the nutrients and the plants go through a quick boom as the plants use up the remaining nutrients in their root systems, it also makes the weed taste better and gives a cleaner high.