Hey, I found an old mercury vapor lamp 175w is there anyway of using this for growing? is there anything its useful for? and also how my gallons of water dose each plant need in my hydroponic system. Thank you.
Mercury vapor lights are not good for growing. They put off more heat than light, and the spectrum is wrong for growing. You could use it to light up the driveway or the yard. That's the kind of thing they're made for.