I am leaving the T5 lights on 24/7, but I was told it was better to use 18on and 6off so the plants could get some sleep. I want to know if I can change the number of hours to 18 on and 6 off without affecting the plants? Would this put them into flowering, or does it take 12/12 to put them into flowering? I am only using 2 4' 4bulb units now, but will have 4 of these units when I start flowering. I am 4 weeks into vegging stage. I look forward to your reply. Peace

4 Answers


Dan Diesel Points7208
hey harley, you will be ok going right to 18/6 , i mess up my light cycles all the time in veg 18/6 then turn light on  on accident when in the 6 hours dark and it does not seem to affect them at all, but maybe i am just lucky??? I only keep a strict light cycle when in 12/12 flowering... good luck bro, keep us posted of your grow,,,you are the reason i am gonna get myself some t-5's , your harvest and last grow has made me a believer in t-5's , i was highley impressed with your results,,,great job, so lets see them again , through your grow if ya do not mind,,,if you make some video's let me know,,maybe you will let me use them and post them on my channel, its called nirvana buds on the share site,,,why don't you join it?? there is nothing on there yet but once they get back to me i will be adding videos of all nirvana buds so people can check out the strains to see what they are buying,,so please join it, it is under recentley created channels,, called nirvana buds,,like i said there is no content yet ,,but there will be soon,,of course if i post your video's on there you would still get full credit,,,peace!!

harley24 commented Aug 25, 2013

Hello Dan Diesel,
I think I will make a video or two on this grow. Maybe three, one during the vegging stage, one during flowering, and one right at harvest. I will be glad to send them to you or whatever I need to do to get them on the site. I will go to the share section and see if I can find the "friend" request thing and get that done as well. I put my girls on 18/6 because Airplane said it may be better to let them sleep for a few hours. I did not do this in my last grow, but I am going to do it now. I always document everything I do, so if there is a difference I will see it. Thanks for the information and I will get over to the share section soon. Peace

Dan Diesel commented Aug 26, 2013

Thanks harley, i am currently on vacation so soon as i get back by the end of the week i will start workin on the channel, and checking out the share vids. So soon as im back i will message you and we can get that going,,,awesome!!!! Thanks again!!!!

harley24 commented Aug 27, 2013

Sounds good to me Dan Diesel. We will earn some points for the videos as well I believe and can spend them on more seeds. Peace


hardnosse44 Points817
harley you are doing good dont worry about stress i do nothing but 18-6 in veg  just cut back your time no need for gradual change   i believe flowering  time is best 12   12   been proven time and time again     NO CANNABIS PLANT I KNOW OF WILL FLOWER AT A 18  6  LIGHT CYCLE    -PS KNOW NOTHING OF AUTO SEEDS PS  DONT WANT TO      HARDNOSE

harley24 commented Aug 25, 2013

Thanks for confirming that. Others have also done that too. I put them on 18/6 because Airplane said it may be better for them to rest a few hours. I did not do this last grow, but I am documenting everything i do and can tell if there is a difference. Peace


Kizmo Points7984
It is fine using 24/0 seven days a week, the 18/6 is better for magnetic ballasts as they need to cool as you would cook the ballast after a while.

But it is safe to run 24/0 and turn to 18/6 as long as you dont goto 12/12 intill you want to turn, you can also go back to 24/0 it wont hurt them,


hip old man Points2824
harley if your already 4 weeks in veg, i would just finish it @24/7 until your ready to filp your lights to 12/12. running T5's or CFL's 24/7 won't hurt most plants! But you can change to 18/6 and it won't hurt them a bit.   24/7 or 18/6 this is up to you.

                                                                               Grow well

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