600 Watt HPS vs 400w MH for veg? Very slow growth, need advice!

ns420

ns420

Active Member
I have been using a 400 Watt HPS Ballast with a 400 Watt Growbright MH conversion bulb (blue spectrum), rated at around 45,000 lumens (supposedly).

I also have a 600 Watt HPS ballast with a 88,000 lumen Eye Hortilux Super HPS bulb (red spectrum).

I was curious as to which I should use for vegging? I know everyone says MH, but in my situation I am starting to feel like I would be better off with the HPS due to double the lumen output and nearly the same heat output.

I have been less than impressed with the 400W MH Conversion Bulb, it seems to run very hot, and has caused heat stress in my 75F 3'x4'x7' vegging room at 12-14" from the plants.

I have gotten very slow growth on a number of my plants on my first run, including a 3" tall White Widow plant that has been vegging for over a month (from seed) and a 9" tall White Widow that has been vegging for nearly 2 months (from seed also). I am using FFOF Soil, Fox Farm Nutrients (following the feeding schedule listed on their website), and my soil runoff PH is 6.5-6.8 and my grow area is a nice steady 75-80F (lights on), 65-70F (lights off). I am currently running my lights 18/6 and have a 424CFM inline fan exhausting outside and moving tons of air through the room.

I am really not sure else what else could be the issue....

Any and all opinions are greatly appreciated. Thanks in advance!
 

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ns420 said:
Hello,

I have been using a 400 Watt HPS Ballast with a 400 Watt Growbright MH conversion bulb, rated at around 45,000 lumens.

I also have a 600 Watt HPS ballast with a 88,000 Eye Hortilux Super HPS bulb.

I was curious as to which I should use for vegging?

I have been less than impressed with the 400W MH Conversion Bulb, it seems to run very hot, and has caused heat stress in my 75F 3'x4'x7' vegging room at 12-14" from the plants.

Any and all opinions are greatly appreciated. Thanks in advance!
Click to expand...
easy one the mh is always better for veg unless you want stretchy ass weak stem plants
 
I added some pictures, if anyone can give me any advice on what I might be doing wrong it would be greatly appreciated.

The plants range from 4 weeks from seed to nearly 7 weeks from seed... and as you can see the growth is far less than desirable.

The tallest plant in the front on the right (that is LST'd) was severely shocked when I transplanted it (overwatered due to bad advice from a friend), and nearly died (had 3/4 of the leaves died off, and the remaining leaves where at least 50% brown), however it has bounced back well and has lots of new growth (I removed all the heavily damage leaves a few days ago, what is on it now is pretty much all new growth from the last 2 weeks).

This is my first time growing ANYTHING, and I expected to make mistakes, but I also don't want to spend another month waiting for the plants to get big enough to start flowering.
 
It can take quite some time for plants to recover from stress, that could be what's going on here with the slow growth.
My first impression when looking at them was heat stress though.
 
Ok, I will go ahead and raise the light up to 18" from the top of the plants (someone had told me that with a 400W that I needed to have the light 10-12" or so from the top of the plants, or they don't get enough light).

My thermostat is on the wall, at about canopy height. Would there be a more optimal place to locate it? I read to not put it in direct light.

If I am getting an improper temp reading it could be hotter than I realize, which combined with having my lights too close would definitely explain things....

I have been watering as soon as my moisture gauge doesn't move when I put it into the soil, and it seems fairly accurate (based on doing the finger test and lifting the pots to see if they feel light).
 
if heats not an issue then use both, that way its getting the best of both, i vegged under 600 hps this time and everything was good but i got some more light for flower(another 400 hps) but when i start my next grow im going 400mh for two weeks till theyre tight and strong and then throwing the 600 hps on it, it gives the plant the full spectrum.
 
oh yeah and throw ur moisture meter out, theyre all shit!! just lift your pot after watering and judge by pot weight.
 
ns420 said:
I have been using a 400 Watt HPS Ballast with a 400 Watt Growbright MH conversion bulb (blue spectrum), rated at around 45,000 lumens (supposedly).

I also have a 600 Watt HPS ballast with a 88,000 lumen Eye Hortilux Super HPS bulb (red spectrum).

I was curious as to which I should use for vegging? I know everyone says MH, but in my situation I am starting to feel like I would be better off with the HPS due to double the lumen output and nearly the same heat output.

I have been less than impressed with the 400W MH Conversion Bulb, it seems to run very hot, and has caused heat stress in my 75F 3'x4'x7' vegging room at 12-14" from the plants.

I have gotten very slow growth on a number of my plants on my first run, including a 3" tall White Widow plant that has been vegging for over a month (from seed) and a 9" tall White Widow that has been vegging for nearly 2 months (from seed also). I am using FFOF Soil, Fox Farm Nutrients (following the feeding schedule listed on their website), and my soil runoff PH is 6.5-6.8 and my grow area is a nice steady 75-80F (lights on), 65-70F (lights off). I am currently running my lights 18/6 and have a 424CFM inline fan exhausting outside and moving tons of air through the room.

I am really not sure else what else could be the issue....

Any and all opinions are greatly appreciated. Thanks in advance!
Click to expand...

i reccomed getting a CO2 generator for veg, put it on the inlet fan, itll work wonders. but u should wait till you get ur plants a little bigger then put them on 12/12
cheers
 
18 inches is definitely going to show you some good results. I keep my thermometer directly under my light, hanging over the plants. Never heard of light effecting a thermometer.
 
ns420 said:
Ok, I will go ahead and raise the light up to 18" from the top of the plants (someone had told me that with a 400W that I needed to have the light 10-12" or so from the top of the plants, or they don't get enough light).

My thermostat is on the wall, at about canopy height. Would there be a more optimal place to locate it? I read to not put it in direct light.

If I am getting an improper temp reading it could be hotter than I realize, which combined with having my lights too close would definitely explain things....

I have been watering as soon as my moisture gauge doesn't move when I put it into the soil, and it seems fairly accurate (based on doing the finger test and lifting the pots to see if they feel light).
Click to expand...

You may want to give them a couple of feet to the light for a little while until you have it figured out, further away only means slower growth so no harm done.
There could be something else going on that effects the distance rule, such as airflow around the light.

Your thermometer is fine, its just that you have to take the plant top temperature with your hand, unless you have an infrared thermometer. Room temp is important too, but sounds like you have that under control.

You may not be watering enough, maybe only due to excessive heat, but don't make any big changes in watering. It's easier to work on one variable at a time, so maybe just changing the light distance first.
 
I have been reading a lot of threads on here about people asking what distance they should keep their lights from their plants, and many people say if you can put your hand at canopy level and it's not hot on the top of your hand it will be fine for your plants... even at 10" it never gets to the point where it's uncomfortable to hold my hand there for a minute or two.
 
Man o' the green said:
You may want to give them a couple of feet to the light for a little while until you have it figured out, further away only means slower growth so no harm done.
There could be something else going on that effects the distance rule, such as airflow around the light.

Your thermometer is fine, its just that you have to take the plant top temperature with your hand, unless you have an infrared thermometer. Room temp is important too, but sounds like you have that under control.

You may not be watering enough, maybe only due to excessive heat, but don't make any big changes in watering. It's easier to work on one variable at a time, so maybe just changing the light distance first.
Click to expand...

Thanks for the advice, I don't think the problem is my watering - though the first 2-3 weeks I was HEAVILY over watering, and nearly killed the two larger/oldest plants (they where the only 2 out of 6 seeds that survived). A month ago I planted 8 more seeds, all of which survived and are still growing strong (although slowly), so I am improving as I learn.

The joys of trial and error!

As far as the airflow issue, I think I have plenty of airflow (424CFM inline exhaust fan that pulls air through my intake from the adjacent room with an open window, and is on a thermostat so it keeps it between 75F and 78F). Though I could be wrong!
 
Single White Pistol said:
That whole hand/heat rule never sat well with me. I can hold my hand pretty close to the light for a while. I never understood it.
Click to expand...

You know I though the same thing, I can keep my hand 6" away from my 600Watt 88,000 lumen bulb for several minutes without it being uncomfortable for me, and placing a plant that close would surely toast the plant.

Though I do have thicker skin than most....
 
18" is the industry standard for a sfe distance from the hood to the canopy.This also allows the light to refract off of the hood correctly,shooting it in all directions.This also allows for the broadest spectrum of light from the hood as it assumes its path downward,spreading as it goes.This is for any size light in the HID class.
 
Light rules my ass...
every grow is different, back off the lights until the leaves perk back up
Yes your plants look like 1 of 3 problems
over water
over fert
or heat( also take a temp measurement in the root zone with a instant read therm)

I am guessing you have just barraged it with light. I say this as that is some righteous internode spacing. Once the leaves perk back up those will be fine. Also they could be slow rebounding from their early life trauma.

As a side note when measuring agricultural stress from light on farm animals what we used was a black painted metal toilet float with a probe thermometer
this modification allows for the effective measurement of the radiative, convective and conductive heat factors. (Note haven't used this since taking lab measurements for a course) but it is quite shocking how much the temp will change when using it vs a naked thermometer.
 
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