I’ve recently been asked by a couple people, how close can you have florescent lights without harming your seedlings/miniature plants? Well, here is where I typically set my light till I’m ready to switch to blurple, I don’t use a tape measure to set it perfectly, I use the back side of my hand and to be honest, these bulbs are cool enough, I’ve allowed plants to grow right up between the bulbs with no issue. As a general rule of thumb though, I go by the hand measurement and the 2 finger standard. Under 24 hours light the lights typically need to be raised every 3 days due to such rapid plant growth