Perfect seedlings????

Refer to a hygrometer, tells you the temp and humidity. Use a heat mat and thermostat.

You can move any lamp the closest it can go by holding your hand under the light at the level of your plants and if your hand feels comfortable after a minute under your light then your girls will also be fine. Cheers

Hey If you're getting stretching you definitely want to adjust the distance...be wary of the hid because they can run so hot. I personally keep a couple cfl lights around just for that young seedling stage, you can keep them so close with rarely any negatives. The t5 is going to be more similar to this and need to be kept close to be any use, not more than a foot. Place the seedlings about 6 inches under it and Place your hand over them to see if you feel too much heat if so keep adjusting slightly so that its close but not hot.👍

Stretching is only a problem if left unchecked. I would personally start somewhere around 24-28" away. If it starts stretching, move the light a little closer. As long as you make appropriate adjustments, there should be no impact longterm. The T5 can probably go a lot closer. Although I have no experience with these lights, I bet you could get within 5" before you have issues, although don't take my word on that last bit.

I find seedlings always stretch even under my 250 watt. Best way I found to get round this is when you have them in the Dixie cups only fill it half way . Then plant your seedling . As it stretches just fill the rest of the Dixie cup up covering the stem with soil . I find this gives a better root system at the start and she grows faster too. I'd recommend using your t5s and just filling the cups up as they stretch . Saves using 250watts of power. But if you must use the 250s then you want them at least 40inches away I'd say. They don't require much light at that stage . Hope this helps