How high

[yooper13]

I recently sprouted a couple bag seed i had, and i have a new 400 watt mh, i am wondering how high i should place the light over the top of the seedlings i have it at about 6 inches now, with a small house fan blowing across them at the low setting ?
Thanks in advance for any reply's.

 

[BudGoggles]

2 ft if there little then gradually bring it down

 

[yooper13]

any opinions on happy frog potting soil? to hot or should it be ok ?
thank you.

 

[Alien Abductee]

yeah a few feet, I usually never lowered my light, I would just let the plant grow into it.. for me that worked. If you lower it too quickly, it can do some serious damage, so I usually play it safe and let the plant decide where to be.

 

[Elite Nugs]

It depends on what type of reflector you have. Your only using 400 watts, so I think 2 feet would be too far. If your reflector is vented, then you can easily have it a foot above the plants. If its not vented, then 2-3 feet from the tops of your plants are good. The main thing here is heat. You place the lights too close, then you'll burn em. Too far and your plants will stretch and not grow as fast.

As for HappyFrog being too "Hot". If your referring to the nutrients inside of it... then no. FoxFarm uses organic nutrients which are close to impossible to run "too hot". HappyFrog is more based around beneficial bacteria. Its a good soil to use, but I would use OceanForrest instead. Has the same thing as HappyFrog, but more. Usually the nutrients that are already in the soil will only last you a couple weeks. Once you start to see light green leaves, then add some nutes.

 

[Alien Abductee]

If he has seedlings, 1 foot maybe too close even with heat removable in my experience at least, without knowing the strain an tolerances.If it has a few sets of leaves, then i think i wouldn't be so cautious. I tend to fall on the side of caution cause im poo' and couldn't get new seeds.. lol

 

[Elite Nugs]

If he has seedlings, 1 foot maybe too close even with heat removable in my experience at least, without knowing the strain an tolerances.If it has a few sets of leaves, then i think i wouldn't be so cautious. I tend to fall on the side of caution cause im poo' and couldn't get new seeds.. lol

I dont know.... Seedlings can take a beating. Now if they were freshly rooted clones, that would be a different story. You can stress a clone out with too much light easily. But seedlings... you can toss those out in the hot sun on a summer afternoon and as long as they have water, they'll stay standing and healthy.

If you keep the light too far from a seedling, then it could stretch so much that it falls over. I've had that happen to me once. So now I keep my T5's inches from them. A 400 watt mh, that vented and one foot away wont hurt a seedling at all.

 

[Alien Abductee]

Well, lets see. A MH 400 watt puts out about 32000-40000 lumens. Light falling off at inverse square, will put the lumens (doing the math) about 9,000 at 2 feet. A plant (or seedling) will start to stretch around 1500 lumens or under. The chance of the seedling stretching while 2 feet under a MH light is really not possible. HPS light, or cfl under minimum lumens maybe. 3.5 feet or more would be the distance to stay below, at least as far as lumens go.

If the bulb is really old maybe, or not putting out the right spectrum. There is a specific nanometer length of blue I think 430 which control how the plant reacts to light. Its the reason hps makes your plants stretch in veg, it doesnt contain the specific wavelength the plant is looking for so it will stretch right into heat stress, left unchecked.

Seedlings handle a range between 3,000 and 10,000 the best, much more than that you risk bleaching, where it turns light green, it will still grow, just not optimal and be under stress.

 

[Elite Nugs]

Well, lets see. A MH 400 watt puts out about 32000-40000 lumens. Light falling off at inverse square, will put the lumens (doing the math) about 9,000 at 2 feet. A plant (or seedling) will start to stretch around 1500 lumens or under. The chance of the seedling stretching while 2 feet under a MH light is really not possible. HPS light, or cfl under minimum lumens maybe. 3.5 feet or more would be the distance to stay below, at least as far as lumens go.

If the bulb is really old maybe, or not putting out the right spectrum. There is a specific nanometer length of blue I think 430 which control how the plant reacts to light. Its the reason hps makes your plants stretch in veg, it doesnt contain the specific wavelength the plant is looking for so it will stretch right into heat stress, left unchecked.

Seedlings handle a range between 3,000 and 10,000 the best, much more than that you risk bleaching, where it turns light green, it will still grow, just not optimal and be under stress.

No offense man, but you may not understand the inverse square law entirely. There is no way that you will get 9,000 lumens directed onto a seedling from a 400 watt MH at 2 feet from the plant. Maybe 9,000 lumens directed onto the entire area the light is covering, which is probably a 4x4 or 5x5 area, but probably not even then.... so then you would divide that by how many square feet that the lights is covering. You also have to take into account the reflector. You are adding the total lumen of the bulb, but half of those lumens are directed up to the reflector and I dont know any reflectors that have 100% reflectivity.

If what your saying is true, then I dont see why anyone would use anything stronger then a 400 watt light. The sun light in the middle of summer, on a clear day with no clouds, around 12pm when the sun is directly overhead... the SUN is only producing around 11,000 lumens.

So again... no offense man, Im not trying to be rude, but your numbers are way off. A 400 watt MH at 2 feet away will be fine for seedlings, but I would go a little closer depending on the reflector being use.

 

[Elite Nugs]

I use HO T5's at about 6 inches from the tops of seedling. My T5's put out over 40K lumens and more of the spectrum is used, when compared to a MH. So not only are they getting more light, but there getting more usable light. They grow fast, dark green, short, thick and strong.