Marijuana
Growing Hydroponic Marijuana Various Extras
growing hydroponic marijuana
index
Carbon Dioxide
EC, TDS, PPM
Heat
Humidity
Media
Number Of Plants
Nutrients
Odors
pH
Temperature
Two Growing Areas
Various Extras
Carbon Dioxide (CO2): Marijuana plants consume carbon dioxide (and expel oxygen) in the daytime hours. During the dark period at night they consume oxygen (and expel carbon dioxide).
When the light is on in a grow room, plants will consume CO2. In a room with little or no replacement carbon dioxide, plants can consume all the available carbon dioxide in an hour or less.
When CO2 levels fall, plant growth slows. Letting in air through a window, door, or other means (and keeping it circulating around the leaves with a fan) will be necessary.
CO2 is measured in parts per million (ppm). The amount of CO2 present in outdoor air will generally range from 350-430 ppm. Away from cities, where the air is cleaner, carbon dioxide will probably be concentrated in lower levels than in the city.
Plants can do well if the amount of CO2 supplied to them remains in the range of outdoor air (350-430 ppm). At levels below 200 ppm, plant growth slows down because the amount of carbon dioxide available is too low.
Increasing the amount of CO2 available to levels over 600 ppm will increase the growth rate of the marijuana plant. Although this does not mean a more potent crop, it will produce a larger harvest in less time than a crop raised with CO2 levels are not in the optimal range.
When the CO2 level goes over 2000 ppm plant growth will slow down because the concentration of CO2 is too high. In order to maximize yield and minimize the length of time till harvest, some growers increase the amount of CO2 to the grow area so the plants have a steady concentration of about 600-1500 ppm when the light is on.
The optimal amount of CO2 will depend on the amount of light available and the temperature of the air that surrounds the leaves. As the amount of light and temperature increase, the plant is able to process more CO2. This results in a quicker growth rate.
Here are some CO2 levels and how they affect plant growth.
Below 200 ppm (Plant Growth Slows)
350-430 ppm (Outdoor Air)
600-1500 ppm (Optimal For Marijuana)
Above 2000 ppm (Toxic For Marijuana)
If possible, maintaining carbon dioxide levels at 600 ppm or higher when the light is on will be best for marijuana plants. Levels between 1500-2000 ppm will not harm plants but even in strong direct sunlight amounts higher than 1500 ppm will probably not be consumed. As levels reach 2000 ppm they start to have a negative effect.
If you have to vent the air out of a grow room with an exhaust system that removes air from a grow room, most (or all) of the CO2 will be removed from the grow area before the plants can use it.
An air cooled lighting system that takes in and exhausts the air from places other than the grow room is suggested when CO2 is being added. Alternatively, a grower could construct an exhaust system that only turns on when carbon dioxide is not being added.
Adding carbon dioxide to a grow room is not something for the beginner to experiment with unless you have a cheap and easily obtainable supply with a means of measuring it.
EC, TDS, PPM, CF:
EC stands for Electrical Conductivity. It is measured in mS/cm (milliSiemens per centimeter). Some EC meters measure in µS (microSiemens). This is simply the EC scale multiplied by one thousand (1 mS = 1000 µS). EC meters are a method of measuring the amount of dissolved solids in nutrient solution.
TDS stands for Total Dissolved Solids. It is measured in PPM (parts per million). It is also a method of measuring the amount of dissolved solids in nutrient solution.
Dissolved solids include metals, minerals, and salts that are dissolved in water. The reason for measuring dissolved solids in a nutrient solution is because if the quantity of dissolved solids is too high, it will eventually kill a plant. When the quantity of dissolved solids is too low, it will limit the amount of nutrients available to the plant.
Assuming you add nutrients according to the manufacturers directions, there will be no chance of the quantity of dissolved solids being too low. However, if the water you use is tap or well water, there will probably be some amount of dissolved solids present in the water. These solids, in addition to the those in the nutrients you add, can cause the quantity of dissolved solids to reach dangerously high levels.
For people that are using well water or tap water, an EC meter or TDS meter is highly recommended. Reverse osmosis and distilled water will have very low levels of dissolved solids, so an EC or TDS meter is not essential. But being able to measure the amount of dissolved solids in nutrient solution, and keeping them within the proper range, will allow you to maintain an optimal level for the plants.
In my case, a good EC meter reading (for my marijuana plants) has been about 0.7 to 1.5 mS (700-1500 µS) during the vegetative phase and 1.0 to 2.0 mS (1000-2000 µS) during the flowering phase. You can increase the EC meter reading by adding more nutrients to the nutrient reservoir. You can decrease the EC meter reading by diluting the nutrients in the reservoir with more water.
A good TDS meter reading (with my TDS meter) during the vegetative phase is about 300 to 700 PPM. During flowering a good TDS level is about 450 to 1000 ppm. You can increase the PPM value by adding more nutrients to the nutrient reservoir. You can decrease the PPM value by diluting the nutrients in the reservoir with more water.
Please note that TDS readings will vary with the brand of meter depending on how it was calibrated. Comparing your TDS readings with someone else is worthless unless you are both using the exact same TDS meter. Comparing your EC meter readings with someone else is not a problem. Take EC and TDS readings after nutrients have been added to the reservoir, then check every few days.
For the first few weeks (seedling stage) the EC or TDS level should be no more than half of what they will be during the vegetative phase. Some strains need more nutrients than others. Aim for EC and TDS readings on the low side of the scale and work up slowly. Optimal amounts will vary with the growing conditions and seed strain, so it's ok to experiment.
If you are going to get a meter to measure the amount of dissolved solids in your hydroponic nutrient solution but haven't purchased one yet, get an EC meter rather than a TDS meter. EC meters are more accurate than TDS meters.
Most EC and TDS meters are calibrated prior to leaving the factory. When cared for properly, no calibration will be needed for a year or longer. You only need to calibrate the meter if you are sure the readings it gives are wrong. If you need to calibrate a meter, it is best to follow the manufacturers instructions.
Note: A CF meter uses CF (Conductivity Factor) scale. This is simply the EC scale multiplied by ten (1 mS = 10 CF).
Heat: Grow lights get hot and heat can be a problem. The more watts of light you have, the more heat those lights generate. Even 250 watt lights can heat a small area beyond acceptable limits.
Most marijuana strains will grow ok in temperatures of 70-80 degrees, and will do best somewhere in between 72-75 degrees, during the day period when the light is on. If the temperature gets too hot it could have a negative effect on the plants by slowing down growth or killing them.
One way to cool the air is an exhaust system that draws hot air out of the grow room. An exhaust system should be able to remove a volume of air equal to the room size every 3-5 minutes. There are also air cooled lighting systems to remove most of the heat produced by lights before the air can affect the grow area.
Alternatives to exhaust systems are air conditioners to cool the air, or adding carbon dioxide to the grow room. When supplied with large amounts of light (over 1000 watts) and extra carbon dioxide maintained at 600-1500 ppm (during the period when the light is on), marijuana plants prefer warmer temperatures.
Humidity: Use a hygrometer to measure humidity if you think your grow area is out of range. A humidifier can increase humidity and a dehumidifier can be used to lower humidity. In general readings between 40-60 percent relative humidity are best.
The humidity should always be kept below 60% to minimize the chances of mold development. If mold is a problem in your grow room, humidity should always be kept below 50%.
Media: Since you aren't using soil in a hydroponic garden, some types of hydroponic gardens (deep water culture, drip systems, ebb and flow systems, wick systems) need a substitute so the roots have somewhere to anchor the plant.
This substitute for soil is referred to as growing medium or media. The media will provide no nutrition, it is just a support for the roots. All nutrition comes from the nutrient solution.
There are various types of media available to grow hydroponic marijuana in. Rockwool is one common type of media, but there are others. Rockwool comes in blocks of solid material that are very similar in feel and appearance to fiberglass insulation used in housebuilding.
There are some types of media that are made up of loose particles like soil. Stay away from these unless your hydroponic garden is designed to use this type of media. Particles can drain into the nutrient reservoir and eventually ruin the pump.
The media you use is up to you. Follow what the manufacturer of your hydroponic garden recommends. If you aren't sure, get rockwool (also known as mineral wool), horticube (for seeds and clones, also known as oasis cubes), or another solid type of media. You can buy some types of growing media in slabs that can be cut to fit into your garden or you can get it in various pre-cut sizes.
There are small rockwool and oasis cubes designed for starting clones or seeds on. You can germinate seeds right on these. Once you've grown a crop or two you can experiment and see if changing media has any effect.
Rockwool and some other types of media should be soaked in water overnight before use. Sometimes this should be water of a certain pH. This is to ensure that the rockwool has a neutral pH level. Follow the manufacturers directions.
If there are no directions, soak the rockwool (overnight) in a clean pot or container with water that has been pH adjusted to 5.5. Next day, discard the water, and fill the pot or container with hot water (pH adjusted) to kill any unwanted organisms that might have a negative effect on your plants.
After a minimum of ten minutes in the water, you can drain the container and wait for the rockwool to cool to room temperature. Once cool, the rockwool is ready for use. It isn't necessary to treat the media with hot water but if you are worried about being clean, give it a try.
Number Of Plants: In many areas, drug trafficking charges are determined by the number of plants being grown. In these areas a plant that produces two ounces (about 56 grams) at harvest time is considered the same as a plant that produces one-eighth of an ounce (about 3.5 grams) at harvest time.
Even if you had a permit to produce medical marijuana for yourself, once you grow more than a set number of plants in certain jurisdictions, you are considered to be cultivating with intent to traffic. So growing 10-20 fairly large plants that will produce an ounce (or more) per plant might be a better idea than growing 40-80 smaller plants that will produce a quarter ounce per plant.
Nutrients: See the page about nutrients and growing hydroponic marijuana to find out how nutrients affect marijuana plant growth.
Odors: Growing (and smoking) marijuana will produce odors. Sometimes they can be strong enough to attract attention of people who don't need to know what you are doing. If you would like to eliminate the smell from growing and/or smoking marijuana, ozone is a good method.
An alternative method is to use exhaust fans, these have the advantage of also being used to remove heat from the grow room. If you plan on using an exhaust system, make sure it is vented to an area that won't attract attention. Placing the exhaust end on a roof or other space that is seldom used by other people is a good idea. You can put carbon filters on exhaust fan ducts to remove odors.
pH: The pH of the nutrient solution should be somewhere in between 5.5 and 6.5 on the pH scale. You will need a pH meter or pH test kit to check the pH and some pH-up or pH-down solution to adjust the pH when it gets out of range. See the page about pH and marijuana if you would like to learn more.
Temperature: Aim for between 70-80 degrees F when the light is on. When the light is off the temperature can remain the same, or drop up to 10-15 degrees without harming the plants. The temperature should never go below 60 degrees or above 80 degrees (even for short periods) or growth will slow down. If these extremes are exceeded for an extended amount of time, the plant may be permanently damaged or killed.
Every strain has an optimal day temperature and an optimal night temperature. The closer you get to the optimal temperature of the marijuana strain you are growing, the better your plants will grow. Strains that originated in cool areas prefer a lower temperature than strains that originated in warm areas.
Some rare strains might like temperatures outside of the 70-80 degree range when the light is on, but almost all will do best somewhere in between 72-75 degrees. Plants grown with large amounts of light (over 1000 watts) and supplemental carbon dioxide maintained at 600-1500 ppm prefer warmer temperatures when the light is on.
Two Growing Areas: An alternative to growing in one area with mh and hps lighting is to set up separate vegetative and a flowering areas.
The vegetative area would use a cloner or something similar that would allow seeds or clones to grow. Light would be supplied by two (or more) standard 24 inch or 48 inch fluorescent bulbs, turned on 18-24 hours a day. Use 30-60 watt cool white fluorescent tubes.
A cloner is a hydroponic based growing unit designed for growing small plants. The openings to place the plants in are close together, so more plants can grow in a small area. When the plants have grown to a point where they are large enough, they are transplanted from the cloner to the hydroponic garden and allowed to grow larger, or they are forced to flower by cutting the light to 12 hours on and 12 hours off per day.
The flowering area would use a standard hydroponic set up with hps and/or mh fixtures turned on for 12 hours a day. While the flowering plants are going through their cycle, another group of germinated seeds or clones will have time to develop in the cloner.
After the flowering plants have been harvested, the plants in the vegetative area are ready to move to the flowering area. New seedlings or clones can then be started in the cloner.
There are three main benefits to this kind of set up. Electricity use will be about 20% to 35% less because the mh or hps light is only on 12 hours a day in the flowering area. The longer a plant has been growing in the vegetative phase, the quicker it will flower.
And you will be able to produce more marijuana because you will harvest about once every 8 to 10 weeks (for most indica strains), rather than only being able to harvest about once every 12 to 16 weeks with a single growing area.
The only drawback I have found is the extra area needed to set up two different grow areas. Since the flowering plants need absolute darkness during the dark phase, the light from the vegetative area can't reach the flowering plants.
These areas will have need to be isolated from each other and other sources of light either by using curtains (or something similar) or by being located away from each other in different rooms.
Any available sunlight will help in the growing process. The vegetative area can be open to extra light at all times but there must be a way to block out all sources of light for twelve hours a day in the flowering area.
----- A plant will die if the roots dry out. Check everyday (or more often) and make sure that the nutrient solution is being circulated properly. Drip systems and ebb and flow systems can keep a plant alive for up to a day (sometimes longer) if the nutrient supply is stopped. A plant in an NFT systems will die within hours of the nutrient solution being stopped and a plant in an aeroponic system probably won't last an hour.
Deep water culture is based on the roots being in the same reservoir as the nutrient solution. There is no chance of the roots drying out unless the reservoir isn't filled. However, the roots must be supplied with oxygen (usually supplied with an air pump). If this supply of oxygen is stopped, the plants will die in several days.
----- Do not use chemicals to clean anything that the water and nutrients will come into contact with, like the inside of nutrient reservoir for a hydroponic garden. Use hot water to clean these.
----- Never touch a metal halide or high pressure sodium bulb with your hands. Body oils will shorten the life of the bulb. If you do touch a bulb, wash it off with a clean cloth that has been dampened with water. Wait till the bulb is completely dry before using, water can cause the bulb to crack. A lit (or hot) bulb can crack or explode if it comes in contact with liquids like water.
----- You can only use a bulb of the wattage you light system was designed for. A 400 watt system only uses 400 watt bulbs. Don't use any other wattage than the one listed on the ballast of your light system.
----- You can use hydroponics to grow outdoors but temperatures must remain within the tolerance of the plant. That means in most parts of the world, you would only be able to grow for several months of the year. Evaporation of nutrient solution can be a problem.
----- When you enter the growing environment. You should be as clean as possible. Taking a shower and changing clothes prior to entering would be a good idea but time consuming. Try to at least wash your face and hands and have clean (lint free) clothes on prior to entry. This will minimize the amount of dust/dirt and limit the chance of contamination.
----- Nutrients, pH, and temperature are among the most common causes of crop failure. Do your best to ensure that they all stay within optimal ranges and you will be assured that you're providing the best conditions to keep your plants healthy, and probably happy.
Related Books Jorge Cervantes' Ultimate Grow DVD
This movie shows step by step instructions covering what is involved in setting up a grow room and growing a crop of marijuana indoors (with soil or hydroponics). It won't teach advanced techniques but it will help you set up your grow room and raise your first crop. There is very little information about growing outdoors, this is for indoor growers.
Jorge Cervantes' Ultimate Grow DVD
Jorge Cervantes' Ultimate Grow DVD 2
Similar to Jorge Cervantes' Ultimate Grow DVD (above), but this version focuses more on growing outdoors. It won't teach advanced techniques but it will help you set up and raise your first crop outdoors. There is very little information about growing indoors, this is for outdoor growers.
Jorge Cervantes' Ultimate Grow DVD 2
Grow Great Marijuana
If you find instructions and books about growing hydroponic marijuana overly technical and hard to follow, this book is a very good choice for simple and accurate instructions. It does not cover advanced techniques so if you already know how to grow, this book would be of little value. But if you are a first time grower with no experience, this is the first book to look at.
It will explain the steps involved from start to finish (with text and images). Includes information on where to grow, type of hydroponic system to use, selecting a seed strain, lighting, fans, nutrients, security, clones, vegetative growth, flowering, harvesting, stress, pests, and more. Recommended for beginners only, this will show you everything you need to raise a hydroponic marijuana crop.
Grow Great Marijuana
Marijuana Grower's Handbook
Very comprehensive book by Ed Rosenthal that covers all aspects of indoor and outdoor marijuana cultivation with soil and hydroponics. A reference manual with over 500 pages and color images throughout.
At the present time this is the best choice if you were only going to get a single book about growing marijuana. Bear in mind this is not a grow guide with step by step instructions. It looks at most issues that a grower will face at some time and is recommended for beginners and experienced growers.
Marijuana Grower's Handbook