A few quick questions (maybe I'm over thinking things)

First question is how many plants can one grow under a 600w MH before needing more light?

Second question is how big should plants be before putting under a 600w MH light?

Third and final question; I am experiencing drastic temp changes, from a low of 58 over night to a high yesterday of 95. I have a fan to put on them to keep temps down but when its on the high only gets to low 70's. Question is how cold can it get before worrying about it harming the plants and how can I stabilize the temp range to stay between 70 and 80 on a constant basis?

Thank you for your help

I thought about getting a small space heater set on a timer to kick on an hour after lights go out and turned on a low setting and kick back off 30 minutes before lights turn back on. Would that be a good option; or would it cause the plants to dry out from too much dry heat?

hmm , id say get a heater , that kicks on when hits a certain tempeture , ill post this right now and answer your others right after this

your plants, well really they can be any size ( minimum id say is 6 inch )

it all depends on the technique, and your grow area

like,plants in some pots, some will need a spacing betwen each other, but other technique like ebb flow table , you put each right beside the other, so agains, depends on wich technique you use, and what space you got .. think you can give me more info so i can give you your answer on how many can fit?

400 watt mh, covers 4ft by 4ft

600 watt , well im guessing 6ft by 6 ft

oooh how big before putting under 600 watt mh light , Bah , you can start it as a seed under that light !

just depends on the height of it , me , 1 inch tall , i got my 400 watt mh at 3ft from it
id say 3-4 ft would be good for your 600 too

Well I got a 6 X 6 X 6 ft tent that I have them in. Light is a 600w mh, digital ballast that can take a hps bulb as well. Soil grow, right now they are in 2 gallon grow bags but gonna transplant when bigger into a 4 - 5 gallon bucket that is square in shape to fit them in tighter together. I've heard you can do 1 plant per sq. ft, and with that thinking I could easily fit 15 inside a 6 X 6 tent with walking room. But not sure if a 600w mh could produce enough light to sustain 15 plants without a rail system. I also thought about using 2 100w cfls on the sides for supplimental lights to help the edges in case 600 wouldn't be enough.

Now I have another newbie question, what is an ebb n flow system?

Well I got a 6 X 6 X 6 ft tent that I have them in. Light is a 600w mh, digital ballast that can take a hps bulb as well. Soil grow, right now they are in 2 gallon grow bags but gonna transplant when bigger into a 4 - 5 gallon bucket that is square in shape to fit them in tighter together. I've heard you can do 1 plant per sq. ft, and with that thinking I could easily fit 15 inside a 6 X 6 tent with walking room. But not sure if a 600w mh could produce enough light to sustain 15 plants without a rail system. I also thought about using 2 100w cfls on the sides for supplimental lights to help the edges in case 600 wouldn't be enough.

Now I have another newbie question, what is an ebb n flow system?

damn , cant bolieve ive been fooled by that double post lol . hmm , https://www.rollitup.org/newbie-central/392514-grow-tent-5ft-10-ft.html

its me asking about it, and all the questions that youll ask yourself lol

Yea, I tried posting that from my phone and it said there was an error so I re-posted. Guess it worked the first time around. I think eventually I'll go and get a 5 by 10 ft. tent, that way I can get a rail system involved. Seems to me that they work better at getting light to the plants rather than having the light stationary, from what I've been reading. Thanks for the comments Bonzing.

The 58 degree low temps aren't a problem, but I'd try to get those day temps down to at least 85 degrees.

You want to have a 10 to 15 degree temp change from day to night for a few different reasons.

As far as the number of plants, that would depend on the method you choose for growing.

Anywhere from 50 in a SOG style grow or 12 -15 if you let them grow to 5ft plants.

If you are growing in a tent, that would limit you as far as space so it all depends.

You want about 50 watts per square, so 6*6=36*50=1800 watts. With one 600 you should be thinking about using less than half the tent and I would say you are looking closer to 8 plants and not 15.

Thanks Japanfreak, I was only gonna use a small portion of the tent for growing purposes so I can have a walk area around all the plants, plus room for my fan, canister and what not. I pretty much was only gonna use the middle area, about the size of 4 x 4 ft. Just wasn't sure if a 600w would be good enough for an area that size, and if 10-15 plants could fit in a 4 x 4 ft area. That would be 24 sq. ft. and if I use 2 sq ft. per plant I should fit 12. I do want them to get about 4 1/2 to 5 ft. tall though.

mhm could be something id do