Growing with 400W in a small closet. All the materials/items described here are available in any hydroponics store or any hardware store. The list of all needed items is located at the end of this page with prices. This guide is designed to create the cheapest setup possible. It will still cost you some money but still far less then most advertised "hydroponics" systems. I am also assuming you can handle a hammer, nails and some duct tape.

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Why do you use Promix and not some fancy Hydroponics system?


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Understand the difference between growing for yield and growing for quality.


First, you need a closet. The closet pictured on the left is an example of an average closet most people have in a condo, apartment or a house.



In order to grow with a 400W light you need to understand that the most this light can cover is an area of 4 by 4 feet (or 120 cm x 120 cm). The area can be bigger as long as you understand that plants will not grow well outside of this area.



In an average closet, you have usually available an area of 4 feet long, 6 feet high and 2 feet deep. This is the smallest area you can install a 400W light. We would all prefer to have a perfect 4' x 4' area and if you do, use it. If you do not, you will be OK with a small closet like the one shown on the picture on the left..



When you close the door of this closet make sure that the closure is tight enough that no light comes in or out.



You can buy a (so-called) Black and White Film, called B/W Poly Film (pictured here on the right), You have to get this from a Hydroponics Store. You will need a piece the size of 10 feet by 10 feet, should cost you under $20. This is heavy plastic film which is Black on one side and White on the other. This is a very good material because its 100% light proof. No, garbage bags do not work, and you can not find this anywhere but a Hydroponics store. The sides of the closet should be covered with Black & White material which will provide you with optimum reflection of the light. When you line up the closet with this material, make sure that the White Side of this material faces the inside of the closet. The FLAT WHITE colour is the best reflective material out there. Aluminum foil or Mirrors will not do as well as Flat White.



The best way to test if this closet does not leak light, lock yourself inside the closet, turn off the lights inside (and turn ON light outside the closet) and check for any lights coming in from outside (and sealing the cracks with tape, get the so-called Metallic Tape, Silver Metallic Duct Tape or sealing caulk).



Cannabis in the bloom stage produce much smaller crop if even the tiniest amount of light gets to it through the cracks in your closet. This is one of the most important and easiest things you can do to maximize your yield, DO NOT ignore it.



To attach the B/W Film/Plastic to the inside of the closet use Sliver Duct Tape Instead of Regular Duct Tape. This duct tape combines an aluminum foil surface with an extra durable rubber adhesive for a long lasting heat proof fixing. Unlike regular Duct Tape, Silver Duct Tape has a highly reflective outer surface that protects the adhesive from the effects of high heat and light that are common in grow room applications. This means that it will never lose grip and your taping will be as secure at the end of your crop as it was at the beginning. Highly recommended. Its more expensive then Duct Tape but its the one to Use, Cost approx. $15/roll. Buy it at any hardware store.


Hydroponics lights produce heat thus the need for ventilation.



The least expensive way to cool down a closet is to simply open the door for the period of time the light is ON and close it when it's OFF. This only works if you have the 400W Light or smaller. From personal experience I can tell you that its better to spend $50 for a small Inline Fan and some ventilation duct then to deal with opening the closet when lights are on. Cannabis has to grow with temperatures between 25 and 30C (75 and 85F). Its true that the heat produced by the lights will be dissipated by the oscillating fan if you leave the door open when lights are ON, but the inline fan will be able to maintain proper temperatures when the doors are closed. This is completely worth it and recommended. Think security, when your guests come over you don't want them to see the closet because the lights are ON and you don't want to cook the plants by closing the door.  


You will also have to fit in this closet an oscillating fan, at least 12 inches in diameter. The fan is designed to provide "Wind" to keep the stems strong and healthy. I would build a little shelf inside the closet and fix the oscillating fan OFF of the floor.


A you can see on the left picture, an inline fan can be attached to the side of your closet through a hole on the side wall. The fan should suck the air out of the closet. The minimum CFM rating (Cubic feet per Minute) should be 50 CFM. Any bathroom fan will do so long the CFM rating is 50 or more. Home Depot sells them for $29.99. Get the one that says 75 CFM, bigger is better.




above you can see an example of an inline fan attached to a closet with aluminum or plastic ducting. This fan can also be attached directly to the hole without any ducting. The air removed from the closet can be directed anywhere, preferably out the window (outside)


This method of ventilation creates Negative Pressure inside your grow space. Any closet, no matter how well closed off from outside still has many tiny holes, whether its under the door, small cracks, electrical outlets, porous walls ... etc. Once the fan is turned ON these holes will provide access for cooler air to enter the grow room. This also allows you better method of smell control since you only have to control one smell source (inline fan outlet) and not many (doors, walls). Just before the Inline Fan you can always install a Carbon Filter which will clean 100% of the smell. With this filter you can take the air exhaust into another room rather then smell... Remember that IF you buy a carbon filter, your Inline Fan has to be more powerful. This means that with Carbon Filter the CFM on your Fan should be at least 100 CFM.


Next, you have to get the 400W light Kit. The KIT consists of a 400W Ballast (or transformer), a reflector and a 400W Bulb. See picture on the below/left to get an idea of what is needed. The Kit should cost between $250 and $350 CAN dollars. The recommended light is a 400W Metal Halide spectrum as this is a Full Spectrum Light. You can also get the 400W High Pressure Sodium Light but its more expensive. Either type of light is fine. HPS or MH .... it don't matter....





Make sure that when you install the light, you can adjust the height of the reflector. The plants should always be around 1 or 2 feet away from the bulb so as they grow, you can lift the reflector higher.


Next you have to get some pots to grow the plants in. In this closet I would recommend 10 plants (or so). Get 10 pots, (3 gallon or 8 inches wide... or bigger)  and fill them with Promix. Generally, any type of pot/container will do just fine. If you get them from a Hydroponics store, get the one that says either 8" (diameter) or sometimes labled as 3 (or 4) Gallon.


Promix is a planting medium (often called soil-less-mix), which on the surface looks and feels just like any garden variety potting soil but is made up of only 3 basic elements; peat moss, vermiculate and perlite. This type of mix is sometimes referred to as the triple-mix.


Promix also contains agents to stabilize the PH levels (measure of acidity) at 5.5 to 5.7 thus eliminating the problem of adjusting PH levels of the water which is crucial to indoor growing.


In other words, so long as you use Promix you do not have to understand anything about PH .. or EC or PPM. In fact all you need to know is that when the plants go dry, you need to add some food to the bucket of cold tap water and feed your plants. Fairly easy I think.




FYI, if you do the same with any other type of (potting) soil, you will have to adjust PH of the water all the time just like in a hydro table.


Promix comes in bails weighing about 40 lb. each ($30) and you get 107 Liters of Soil-less-Mix. This is enough for 6 months for a small closet. Happy Girl does not make this product and we do not intend to implicate the manufacturer with our activities but the simple fact is - this product works for us and we love it.


Promix can be found across Canada and US in different garden stores. So far, we can confirm that Promix BX and Promix HP sold only in large bags as well as Sunshine MIX No.4 in black bags is ok to use.





Call some Rona Hardware or Home Depot stores and most will have it, but not all. Also available at all Hydroponics Stores.



This is a list of Items needed to create a closet.


400W Light Kit for $250 to $300.


Roll of Silver Duct Tape for $15,


10 feet of B/W Poly/Film for $20,


Oscillating Fan for $30,


Inline Fan for $100 to $150,


Venting Duct from $10 to $30,


Bail of Promix for $30,


Pots for $10 to $20,


Timer $15-$25,


Seeds for $60 to $100.

Total cost of this project is from $400 to $500 dollars.


Of course you do not need a new oscillating fan and the ventilating duct can be bought cheaper then quoted here. However, you can not cut corners when it comes to the Silver Duct tape or the actual light kit. No, you can not use just any 400W light, it has to come from a Hydroponics store.



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