Going from T8 to T5 HO fixture. Proper distance from plants?

dustonj2008

dustonj2008

I recently upgraded my old 4' T8 dual bulb fixtures. I ended up picking up a Hydrofarm T5 HO EnviroGro 4' 8 bulb fixture and filled it with AgroMax T5 HO 6500K bulbs. I've noticed a pretty obvious increase in brightness and heat from the upgraded fixture. Most of the seedlings seem to be responding very well to the new fixture. That being said, I am starting to notice a little bit of a purple color on some of the seedlings:
 
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I am thinking that I may have had the light fixture too close. It was at about 4" over the top of the seedlings which has now been bumped up to 6". Also, the other night I believe that I accidentally flipped the light timer switch to manual so the lights were on overnight which probably didn't help.
 
Does anyone have any advice on distance with T5 HO fixtures? Am I missing anything? I appreciate everyone's help in advance.
 
Thanks,
Josh
 
I doubt the "purple" color is from the lighting as my starts are under same lighting.  You want the fixtures as close as possible if max growth is what your wanting without burning the plants.  With good ventilation that can be as close as an inch but you will need to constantly adjust the lights as the plant grow.  I normally set my start lights at +4" and adjust every few days.
My guess is your soil nutrients need adjusting?  Whats its PH and how moist are you keeping it?  Also may want to ditch the peat pots for peppers, many varieties cannot handle peat well.  I use them for my starts but once true leaves are formed I rinse all peat off and move to my growing soil.
 
Also, I've never had good lasting results with rockwool as a grow medium, other have, just not me.
 
BTW the hydrofarm lights are awesome to germ plants on!
 
I've been keeping the peat pellets pretty moist. I may be over-watering a touch to be honest. I regret my decision to start them in peat pellets after hearing about how quickly they dry out among other things. I plan on potting up into soil once I get my second set of true leaves. Do you think I pot up after the first set of true leaves instead?
 
As far as PH, I couldn't tell you what the PH level is for the pellets or rockwool. I didn't know it was necessary to test the PH this early. I haven't been adding any additional nutrients to my water. Most of my seedings do not have true leaves yet.
 
Fluorescents don't put out a great deal of heat, so put them as close to your seedlings as possible. Too far away and they'll be leggy. Don't worry about nutes until you pot them up. You could damage the roots if you fert too soon. Besides, the light is their main food source.
 
As a general rule, I put my hand on top of the seedlings and lower the light to where I just feel the heat from the lights on the top of my hand and adjust it as they grow.
 
You will get purpling of the leaves from the lighting intensity.  Doesn't hurt them tho.  Keep em the same distance you had em from the T8's.  
 
I added some new 4ft T5s this season, and they are much hotter than my T8 shop lights. This may just be a property of the unit, but I had to raise the lights quite a bit more than with the T8s - especially in the beginning. Now, they are at least 6 inches above the tops of the plants, maybe higher. Any closer and it starts to toast the foliage and dry the soil quickly. I can let the plant tops touch the T8s. I also saw a bit more purple-ing in the beginning and thought I mismarked some seeds!
 
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hottoddy that's the same fixture I have other than I got the 8 bulb model. It sounds like that's probably what it then. I had my T8s RIGHT on top of the seedlings and didn't have this effect. When I upgraded to the T5 HO I noticed my thermometer spiked into the 90s so I moved it up to 4" off the top of the canopy. I thought that was enough but apparently 6" + off the top of the canopy might be ideal for this model. Thanks for the info! It's nice to know I'm not the only one that had this exact same issue.
 
Cheers!
-Josh
 
You will definitely get purpling with light intensity, but as stated it doesn't hurt them and will in fact go away. Genetics also plays in.

My babies in my main tent are about a foot away from my led panel and all are a nice green except the CGN21500 which is now nice and purple. Cotys and all.
 
I was expecting my Pimenta Puma seedling to have a purple hue. I wasn't expecting to see the cotyledon's of my Reapers, Red Bhuts, Trinidad Congos, Big Sun Habs, etc. Is this normal for these varieties? Also, how long does it normally take for the leaves to recover? 
 
It's just the plants version of a suntan. My T5 HOs are about 6" off the top of my plants. Big difference between T8s and T5 HO. They get pretty warm but everyone's heat factors are going to be different. I would start them around 6-8 above the plants and check the temp and how the plants react. Then raise or lower from there. I have wireless temp probes on my plant rack. There is a 10-15 degree difference between my T5 shelf and the LED one. 
 
Just to illustrate, this is my CGN21500 right now lol. Same distance as all my other plants--about a foot, maybe a bit more--from my LED light, and its the only one that purpled up like this.
 
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