Hello, I currently have 4 NL's and 1 UFO blue widow under a T5 2, 4' tubes and a couple fluros, they are 5 days old and are all looking healthy except 2 that are stretching a little. I've read that putting young ones under a 400w HPS is to much, so how old should they be before I switch?
Hey, I would say keep them under the T5 for the next 2-3 weeks, if they look like they're stretching move the light a little closer down T5's can be place very close to the canopy. You can put sprouts/seedlings under HID's right away just have to make sure the light is high enough usually 2ft for sprout/seedlings and sprouts/seedlings can be placed around the perimeter of the light for the next few days and gradually moved under the light. Goodluck.
i would keep them under the t5 for a couple weeks. you can get that t5 as close as you need to help prevent stretching. when you do put them under the hps just make sure it's about 2-3 feet above the plants like ncdrogro said for the first few days so they can get used to the HID. good luck check out my grow http://forum.grasscity.com/general-indoor-growing/531815-1000w-mh-hps-lst-scrog-dwc-first-grow.html
Thanks for the feedback, I'm going to keep them under the T5 for a couple more days then switch it with the HID.