Here again for more advice (veg light)

So, I was just allowed a 4x4 flowering tent (a new cat can get you everything). I already know I will be running either a Mars II 900W or Mars reflector 960 in there along with my two mars 300W panels, but I need advice on best VEG light for my 2x4x5 tent. Can’t decide between T5 or a CFL with reflector. (or whatever else is best, please enlighten me on what YOU would do).

2x4 tent will be for vegging/seedling


This is alot of info. Copy and paste it into a file for future reference


There are three major types of lighting systems available right now for growing marijuana:incandescent, fluorescent, and high intensity discharge. Incandescent lights are horribly inefficient (especially the screw-in “grow bulb” type) and really not an acceptable option for marijuana plant growth. Although they are inexpensive to purchase, their cost of operation makes them the costliest source of light. Therefore avoid at all costs.


Until the early 1980’s most indoor marijuana growers used fluorescent lights to illuminate their garden. These tubes have tremendous advantages over incandescents. They emit about 3 times as much light as an incandescent (given the same wattage), and the light spectrum is one that plants con use more effectively.

However, they do certainly have their limitations. Light is emitted over a large area, so it is not concentrated. Because of this, the lights have to be hung very close to the plants, and constantly moved to accommodate plant growth. This makes garden maintenance rather difficult. Marijuana plants can often grow very quickly increasing the times the lamps need raising. To add to this, in the flowering period, fluorescsent lights are not effective making them a poor choice for lighting marijuana plants.

Fluorescents are, however, very useful in cloning, and starting seedlings. Because in these stages, a plant is not growing vertically very quickly, the disadvantages of moving the lights are reduced. They also put out a more gentle light than the HID lamps, and release less heat.

If you choose to use fluorescents, it is best to purchase the ‘cool white’ variety or a mix. The ones that are sold as grow lamps (including grow-lux, vitalite, etc.) are much less efficient than a standard fluorescent, and just do not put out enough light to be useful. The slightly different spectrum produced by these lamps does nothing for most plants.

High Intensity Discharge Lamps (HID’s)

You will find pictures of marijuana lights here.

High intensity discharge lamps are easier to use, and more efficient. Low wattage HIDs are sometimes sold for household outdoor use.Large Wattage lamps are used for lighting streets, parking lots, stadiums and other large areas. They come in two basic flavors:

Metal Halides or MH lamps emit a white light that looks slightly bluish. They are used to light stadiums, convention centers, gymnasiums, and other large areas where a natural looking light is desired.

High Pressure Sodium or HPS lamps emit a pink or amber light. They are used for lighting parking lots and other areas where the color of the light is not important. HPS units are much more efficient than MH ones, producing more light and less heat per watt of energy consumed. They are often used alone with no detrimental effect on the plants, and will promote faster plant growth than MH lamps during both vegetative growth and flowering. Combinations of
bulbs are NOT required, as the HPS lamp does produce all of the light spectrums necessary for healthy growth.

MH lamps are available in 175,200, 400 and 1000 watt sizes. HPS lamps come in 50, 75, 150, 400 and 1000 watt sizes. Each lamp requires its own ballast, which comes with the fixtures that are designed to use these lamps, and are also available separately.

The following chart shows how much light each lamp emits, and the area that it covers adequately:

Timers for the garden

The lighting system needs to be switched on and off automatically so the marijuana plants receive 18 hours of light per day during vegetative growth and 12 hours per day when flowering. most hard ware stores and other electronic shops sell timers. they are usually very cheap . It may be advisable however to purchase a more robust timer if your serious like a pool timer.

Lamp # of Lumens Sq. Ft

4’FL (CoolWhite-40W) 2,960 1-2
8’FL (CoolWhite-75W) 5,800 2-4
MH 175W 14,000 5-10
MH 400W 40,000 12-20
HPS 70W 7,600 3-6
HPS 150W 16,000 6-11
HPS 400W 50,000 15-30

Marijuana grow rooms should receive 1000-3000 lumens per square foot. Successful gardens usually are lit at around 2,000 lumens per square foot. During the vegetative stage, plants stretch out when they receive low levels of light. During flowering, the flowers are looser and sparse.

When choosing which marijuana lights to use in your garden, we suggest a combination of MH and HPS with flouros used in cloning and early seedlings. It is also important to chose the right shade. Some will reflect light much better than others. Any good supplier should be able to recommend the best for your requirements.

Thanks for your reply, I am not interested in MH/HPS because of heat. My room temp is already pretty high and the 4x4 is not even here yet, more wondering what would be best between fluo’s and cfl’s since they are low temps lights

Measure the inside dimensions of your tent, and see how a 4’ t5 fixture will fit. Most of the fixtures I’ve seen have been about 4’ on the money. If your tent is exactly 4’ or smaller, that big of a fixture won’t fit well. If you find that a 4’ fixture will fit inside your tent reasonably, that will give you pretty even coverage.

If you can’t go with a 4’ fixture, t5 to CFL is probably going to be a crap shoot. Most 2’ fixtures won’t have the output to fill the tent, and two fixtures probably won’t fit. Two of the 125-150 CFL grow lights would probably fit and do the job, but bulb replacement is usually more costly.

If you’re limiting options between the two, that’s pretty much where your decisions will be. If it were me, I’d probably go with the CFL if 4’ t5 won’t fit. But I would also plan on having to buy another cfl fixture at some point. Hopefully that helps!


I think this is what your looking for. It’s LARGE so copy and paste to your filrd for future reference ok


Ideal solution for your makeshift PC tower grow box, cupboards and similarly confined spaces;
They run at considerably cooler temperatures than traditional light fixtures. That makes them considerably safer due to lower fire hazard;
Their chiller temperatures also mean that they do not need too much external cooling to stay at normal levels.


Not particularly strong. HID light fixtures are considerably more powerful, so consider these if you are after bigger grows;
Unsuitable for larger grows.

Like everything else in marijuana growing, it all comes down to your personal needs and preferences. There is no one stopping you from installing an HPS lamp in a 2’x2’x4’ closet (good luck with that!), but this is the consensus among growers from all over the world.
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Your objective when buying CFLs should be to purchase the wattage (W) that is the highest possible for your grow area. Usually, more wattage means more power, which in turn means more light, and thus, more food for your plants. If you want to determine the suitability of the lights, you will want to also check the lumens (lm) to understand their output.


Generally, each plant should be covered by around 10,000 lumens. So if a standard CFL bulb gives off 2,500 lumens, you’d need 4 or more of those, until you reach the desirable levels. CFLs come in 15, 26, 42, 65, 68, 85 and 105W versions, although larger models do exist. A 42W CFL lamp (the best you can use for marijuana growing) emits about 2700 lumens. Four 42W CFLs use 168W and emit 10,800 lumens. More powerful CFL lamps maintain a similar Watt/lumens ratio, so you get the picture. You can easily check the lumens of your light by using this handy calculator here. It is generally advised to keep using CFLs until you reach 250W of power. Anything more than that is overkill and you should probably consider switching to a more powerful light. Remember, CFLs are more suitable for small-scale operations.

But that’s not all; this is where the Kelvin scale comes to play. For those who skipped our lighting tutorial (shame!), this scale is used to measure the “color temperature” or “frequency” that is emitted by light bulbs. Marijuana plants love red and blue light, so you are basically looking for bulbs that are as close to that as possible. Interestingly enough, HPS lamps emit light that is mostly in the yellow spectrum (meaning that most of it goes to waste). And this is where the CFLs shine (pun intended): although they are much weaker People who should go for CFLs

People who want to grow a plant or two for personal use;
People who have turned their obsolete PC tower or their grandma’s commode into a grow room;
People who want to try growing a plant but don’t want to spend much.

On the other hand, if you are looking for massive yields and a more automated growing setup, steer clear of CFLs. The rule of thumb here is that when you need something more than 250W of power, you are better off with some other type of light. We have a whole section for you to choose what suits your needs best!
A little bit of science

There are a lot of variables to consider when choosing grow lights. Grow light science can confuse you a little bit at first, but after a while, you should know what you are looking for. If you want to learn more about the scientific jargon, it is strongly suggested you do so by visiting our relevant page. If you believe that you are fairly knowledgeable about the facts below, you can skip this part and go straight to the shopping list. The rest of you, take a deep breath and follow us to the exciting world of lighting science.
Wattage and the Kelvin Scale
than HPS lights, the amount of usable light they emit is higher than theirs. As we have repeatedly written in this website, different growth stages require different light spectrums. Check the package for the Kelvin spectrum indicated and choose accordingly.
The 2700K spectrum, means that they are a perfect choice for the later stage of plant growth.

26W – 2700K bulb, equivalent to a 100W incandescent lamp;
Lumens: 1700lm;
Lifetime: 10.000 hours;
Size: 2 x 1.2 x 0.3”.

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CFLs come in 2700K, 3000K, 4100K, 5100K, and 6500K models. Bulbs on the lower side of the Kelvin scale, like the 2700K, are more suitable for the later stages of plant growth, while 6500K ones are better for vegging. If you use the in-between spectrums, then you get a nice and balanced result by modifying the rest of your bulbs accordingly.
Every indoor growing light ever is designed to mimic the sunlight. In nature, the sun produces different rays in the spring and summer (blue, vegging) and different rays in the autumn (red, flowering). The sun also produces green, and orange rays, but cannabis plants do not use them.

Warm white bulbs offer the red-yellow spectrum of light, which is ideal for the flowering stage.
Cool white bulbs produce more blue spectrum light and are good for the vegetative state.

Vegetative Stage – 5000K / 6500K


Bulbs that are more blue are called “Cool white” or “Daylight” colored and are listed with a Kelvin of 5000K / 6500K. These “high kelvin” bulbs are optimal for vegetative growth when your plants naturally need more sunlight.
Flowering Stage – 2700K


Bulbs with a more yellow/red tint are listed as “soft white” colored with a Kelvin of 2700K. These “low kelvin” bulbs are optimal for the flowering stage when your plant thinks that winter is coming.
Some Great CFL Models

Here are some of our favorite CFL models and their specs. Although there is no reason to be overly picky with your bulbs when growing with CFLs, these fixtures are ideal to get you started.
Agrobrite T5 4′ 4-Tube Fixture – EnviroGro


This model comes two sizes: 2’ (23” x 13.5” x 3”) and 4’ (48.5” x 15.5” x 4.2”) and five patterns (2, 4, 6, 8, 12 tubes), offering you a wide range of customization.

High efficiency specular aluminum for maximum reflectivity;
Can be hanged in three ways: overhead, vertical or horizontal;
10′ grounded power cord;
Includes 4 fluorescent 6400K, T5 tubes, that make this fixture ideal for the flowering stage of your plants;
5-year Ballast Warranty, 1 Year on material and workmanship.

Apollo Horticulture 5-Pack of 2′ T5 Bulbs – 2700k and 6400k


These tubes come in both 2700K (bloom) and 6400K models (growth), so you can pick whichever suits your needs, according to your plants’ stage of development.

Package Includes 5x T5 Light Bulbs of 24W Each;
Size: 23.5” x 4.6” x 2.6”
Color Temperature – 2700 K;
Lumen – 2,200lm;
Dimensions: Length – 22.12″ / Diameter – .62″.

Dayspot 26W, 6400K Bulb – Hydrofarm


This CFL spiral bulb provides you with all the light you need, while at the same time reducing energy costs.

26W – 6400K bulb, equivalent to a 130W incandescent lamp;
Lumens: 1600lm;
Lifetime: 10.000 hours;
Size: 6 x 2.5 x 2.5”.

Sun Blaster 26W, 2700K Bulb – Future Harvest


The SunBlaster 26W CFL light bulb was designed with growers in mind. They will fit in almost any light fixture and they their output is equivalent to that of a 100W incandescent light bulb.

How to Use CFLs for Cannabis Growing

If you still believe that CFLs are what you need, then we are assuming that you have a limited space to work with. Therefore, the following tutorial will be focused on growing a single plant. In reality, this is a short tutorial on growing small with CFLs, but there are some useful lessons along the way. If you are completely new to growing, you are advised to carefully read our in-depth tutorials and visit our forums. This will solve 90% of your questions. Go on, we’ll be waiting.
The Basics

Back already? Assuming you have done your homework (or at least have grown -basically any- plant before), you know that houseplants need three things in order to survive, in this order: light, water, and nutrients. Marijuana plants go through three major stages of development that are universally acknowledged among cannabis growers: seeding, vegging, and flowering. All these transitional phases are determined by distinct patterns in the lighting cycle . In reality, there are many transitional periods that are also important, but these three should be your main focal point (at least for now). You can find more on marijuana grow phases here. Cannabis plants have no pre-determined sex. Therefore, you should make sure that the conditions you provide promote the development of female plants (the ones who provide you with smokable buds). More on that here.
Reflective Material

In order to make the maximum use of the light from your CFLs and reduce light leaks, you will need to cover your grow space with a reflective material. These will distribute the lighting more evenly across your plant, ensuring that no corner will be left in the dark. Even the best of grow lights can not penetrate the whole of the plant on its own, so some reflection is needed. Mainly, you’ll be looking at these options:



Pros: Durable, easy to maintain, 90-95% reflection



Pros: Popular, cheaper, 92-97% reflection (2mm version)

Matte white paint


Pros: Cheap, can be found anywhere, 80% reflection

Panda plastic


Pros: Easy to clean, perfect short-term solution, 80% reflection

Orca Grow Films


Pros: Mold resistant, easy to clean, expensive, 95% reflection

All of these options are readily available online or at home improvement stores. However, consider opting for the easy solution, which definitely a grow tent. It comes as pre-built setup and it will be already insulated and coated with reflective material. If you are impatient or not quite the handyman, check out the offers by Dealzer and Superlcoset. Grow tents are versatile, cheap (contrary to grow boxes) and they have been designed with growing in mind.

Here is where things get interesting. Assuming you want to grow just one plant, you need at least 150W of CFL power. Although you can play around with the lighting, the optimal CFL arrangement would be 2x40W 5000K-6000K bulbs + 2x40W 2700K bulbs. You are welcome to experiment, but this is the foolproof approach!
Things to take into account

CFLs’ light penetration is poor, so, many smaller CFLs are more effective than a few big CFLs. Their light can be spread more easily (although you should cover your grow space with reflective material beforehand). 4 x 40W CFLs (160W) will get bigger yields than 1 x 200W CFL.
CFL bulbs under 40W are usually a waste of money. On the contrary, 40W+ CFLs are ideal for small scale growing (up to 250W).
At this scale, power is more important than Ideally, you’ll want to combine the two (and frankly, that is not too difficult to do). Getting more juice should be your top priority. However, learning one or two things about spectrum along the way can’t hurt, so we will expand upon this subject in the following parts.

Set Up

We started this article by stating that CFLs are the masters of growing in confined spaces. So, here is a list of grow rooms that CFL bulbs would thrive in.



Any old furniture will do if you have the patience and skill to turn it into an adequate grow room. Just be sure to properly insulate it. More info and how-to’s here.

PC Tower


As the era of tower PCs is drawing to a close, it would be wise to find a new use for your old friend, with whom you spent hours of playing Quake 3. CFLs make great sources of light for a modified PC tower (more info on how to turn one into a grow room here).

Grow Tent


Cheap, flexible and reliable, grow tents are by far the easiest solution if you are looking for a portable grow room. Check out our friends at Dealzer and SuperCloset for some really cool models! Just be sure to stay around the 2’x4’ range if you want to start small.


Germinate your seeds and plant them, or just plant your clones;
At this stage, your plants should follow an 18/6 light cycle (that means 18 hours of light, followed by 6 hours of darkness). You probably do not want to do that yourself so get a timer for your CFLs;
Water your plants adequately (DON’T water them too much) and watch them reach the vegging stage.
Pro Tip: CFLs are awesome for the first weeks of life of a grow, especially seedlings. Regardless of their setup, many experienced growers prefer to use CFL in the first few weeks, so that they can reap the maximum rewards of CFLs.



This is where things start to get serious. Your plant is basically just a baby at this point, so treat it like one! At this point, the plants need more daylight and therefore require “Cool white” or “Daylight” colored bulbs, that run at 5000-6500K.

Water it regularly (do not DROWN it);
Adjust your CFLs so they are within 4″ of plants (try not to burn them though). The rule is: if it’s too hot for your hand, it’s too hot for your plant!
Give nutrients (but not too many of them);
Train your plants to use as much space as possible. You can find extensive tutorials here;
Again: don’t overwater or overfeed your plants;
Don’t panic! – most plant problems are easy to fix.

Remember that plants are growing rapidly at this stage, so give them a bit of leeway so they don’t grow directly into the lamps. A good all-round solution is to train them. Not only do you reduce the risk of your plant crashing on your light bulbs, but you will also dramatically increase your yield. Training is a big part of a successful grow and it we have covered it extensively here at HTG. Here is a list of all the training articles we have presented on this website

Bending Parts of the Plant
    Low-Stress Training
    Super Cropping
    Monster Cropping
    Screen of Green (SCROG)
    NFT Nutrient Film Technique
Pruning of the Plant
    Sea of Green

Tips for efficient CFL vegging in a nutshell

Plant Training;
Adjust CFLs Regularly (daily if possible);
Keep CFLs Close – 4″ away from the top of your plants should do it (remember the hand/plant theorem!). Try to manage your space so that all parts of the plant are within 8-10” of a CFL bulb;
No part of your plant deserves to be in the shadows. Be sure that light is distributed equally;
Try not to move your plant around a lot;
More Watts=More Light=Better Results.



When you switch your light schedule from 18/6 to 12/12, your plant will enter the flowering stage, responding to the fewer hours of daylight. This effectively tells your plant that it is time to reproduce because it’s going to die soon. At this point, you should run a check so you can make sure that absolutely no light enters your grow room during the dark period. Not even tiny blimps from electric devices. At this point your plants require bulbs with a more yellow/red tint. These are often called “soft white” and are colored with a Kelvin of 2700K. These “low kelvin” bulbs are best suited for the flowering stage, since your plant is getting ready to flower before winter comes.

Tips for efficient CFL flowering in a nutshell

Give your buds all the light you can – CFLs can work wonders at this point. Just keep them as close to your buds as possible (without burning them) and watch your plant yield like crazy;
Keep the temperature at adequate levels – If you read our tutorials, you probably know that temperature control is one of the cornerstones of proper growing. However, the flowering stage requires a bit more attention. Be a little more careful and, if possible, have a small fan blow gently on top of them.
Training is over – This is not the right time to train your plants. Generally, you should do that in the vegetative period.

When your plants’ buds fully develop, then it’s time for harvest. Lighting has nothing to do with harvesting, so for that, Just be patient and cure your buds properly!

Tip: If budget is not a problem for you, think about installing an MH lamp in the last week of budding. Many growers believe that it can improve the quality of the bud.

Hope this helps


1 Like

Thanks dbrn32, like you said 4’ fixture wont fit the 48" tent. Was looking at timber grow lights, i think im gonna build a 4 cob 200W cree fixture in 6500K’s. Do you think that would outbeat the T5/CFL’s? I would be able to make my own fixture and get the coverage neeeded.


It’s definitely going to provide a lot more light than any of the fluorescent options. Probably more than is needed for veg light. If you were going to drop the cash on something like that, I would consider getting it in a flowering spectrum and using it there. Then looking back into a more affordable option for vegging.

Hi. I’m running a 600 watt MH in the 2nd week of vegetation at 50%. The ballast has settings for 50, 75, 100% and super lumens. When should I increase the %? Thanks…