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Hydroponic Marijuana Grow Guide

How to Grow Hydroponic Marijuana

The best marijuana growing guide we have ever seen in our 19 years online. Our readers get a $10 saving use code STICKY420 – Click here


What is Marijuana Hydroponics and How to Grow Weed with Hydroponics?

In Latin, the word hydroponics means literally “water working.”  Growing marijuana with hydroponics is the practice of growing plants in either a bath or flow of highly oxygenated, nutrient enriched water. Growing marijuana hydroponically simply means that you grow the plants in an inert, sterile growing medium instead of in soil. All of the plants’ nutrient requirements are supplied when you mix water with the nutrient solution. Hydroponics introduces the water, nutrients and air to the roots through the growing mediums and since using hydroponics bypasses the web of roots and the energy required for the plant to acquire the nutrients you get faster growing plants.

 Hydroponic system
Plants are 80% to 95% water; the remaining parts are carbon, oxygen and hydrogen. Plants extract these elements from the air and water so nutrients are actually a very small amount of the total weight of a plant. It is the plants entire atmosphere that needs to be controlled within the hydroponic environment to produce perfect crops. Additionally, very little water is lost to evaporation in a hydroponic system, owing to its application in drought stricken areas.

Nutrients 101

Marijuana plants, and in fact all plants, do not need to be in a living soil, they require nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg) and sulfur (S). Those are the macroelements (the big ones) and the small elements known as microelements are iron (Fe), chlorine (Cl), manganese (Mn), boron (B), zinc (Zn), copper (Cu) and molybdenum (Mo). Growing marijuana indoors with hydroponics, water is enriched with these very same nutrient salts, creating a hydroponic nutrient solution which is perfectly balanced. An all purpose hydroponic nutrient solution with secondary elements like calcium, sulphur and magnesium and trace elements boron, copper, molybdenum, zinc, iron, and manganese will get you through all stages of growth. But depending on the stage of growth, you can adjust different nutrient levels needed at different times to optimize your yield. A 15-15-15 solution contains 15% Nitrogen; 15% Phosphorus; 15% Potassium. A 20-10-5 solution contains 20% Nitrogen; 10% Phosphorus; 5% Potassium. The percentage of the solution not used by N-P-K is trace elements and inert material.  If you are buying hydroponic nutrients, get the powder kind that mixes with water. It is much cheaper over the long run when compared to pre-mixed solutions.

NPK nutrients

N = Nitrogen
P = Phosphorus
K = Potassium

  • Higher amounts of N are needed when the temperature will be below 80 degrees in the grow room during vegetative growth. 20-20-20, or 23-19-17, or 12-6-6, or something similar, with trace elements should do it.
  • If temperatures are higher than 80 degrees in the grow room, you need not worry about more N in the formula during vegetative growth.
  • During flowering the plant needs lots of P, regardless of temperature. 15-30-15, or 5-20-10, or 2-4-3, or something similar, with trace elements should do it.
  • Do not over fertilize your plants as too much fertilizer will kill your plants. If you under fertilize, plants will take longer to grow but will not die. Follow the mixing instructions on your hydroponic solution package, if you aren’t sure, use less rather than more.
  • As water evaporates it is absorbed by the plants, your water reservoir level will drop. Add tap water that has been aged 3 days or longer to the reservoir. I don’t add nutrient solution when I top up the tank, some people do.
  • Change the nutrient solution every 2 weeks. That is, discard the old solution and clean out the reservoir, pumps, and other equipment that is used with HOT WATER. After cleaning, add tap water that has been aged 3 days or longer to the reservoir then add nutrient solution. You only need to clean the cups and tubing the plants are in before you start a new crop.  More detail on nutrients.

Marijuana nutrient cycle

The timer that starts to pump the nutrient solution should turn on and the solution should submerge the plants roots about every twenty minutes. As soon as the roots are submerged, the pump can shut down. If it takes longer than 20 minutes for the roots to get water, the roots will usually grow long, and they can grow very long looking for the nutrient solution source. In fact they can grow so long and thick that they prevent the solution from reaching all the way up your grow cups. This will also raise the chance of root material being ripped out and clogging the system. Once the flow is clogged by root or other material inside, you will have to take the garden apart and clean it.

Check the root length every few weeks. If it is hard to remove the cups the plants are in because the roots are anchored to the internal channel, the roots are too long. The root should be short enough to not touch the narrow point where the solution enters the cup holder. If they are too long, trim them down with scissors. Make sure they are not going too far, but don’t cut unnecessarily.  The old solution that you are discarding can be used to water house or garden plants. This will at least double the growth rate if you usually water your plants with regular tap water! More detail on nutrients.

Why not soil?

In soil, biological decomposition breaks down organic matter into the basic nutrient nitrogen, phosphorus and potassium salts that plants feed on. Water dissolves these salts and allows uptake by the roots. For a plant to receive a well balanced diet, everything in the soil must be in perfect balance. Rarely, if ever, can you find such ideal conditions in soil due to the lack of organic matter left behind on the surface, contamination and biological imbalances.

Soil is not able to produce a high volume of nutrients as hydroponics can deliver. Hydroponics takes the desired amount of food directly to the root rather than making plant’s roots look for it. Soil loses its nutritional value and is difficult to measure in terms of pH and fertility. With hydroponics the pH and nutritional value of the water are easily measured and maintained, so plants always have enough to eat. Only when you water your soil plants, the basic elements can dissolve into the water. In a hydroponic system, moisture is present for extended periods of time or for all the time. In addition, soil plays host to many nasty little creatures, pests and diseases while hydroponic growing mediums are inert and sterile making a very hygienic environment for the plant and owner.

Indoor marijuana

Hydroponic marijuana set ups

All growing described on this page is done using the Ebb and Flow system. The Ebb and Flow system is one of, if not the most popular hydroponic methods for growing weed. It is simple and easy to use. It works like this: A reservoir containing nutrient solution is located below a growing tray. To support the plants in a hydroponic system, an inert soil-free medium like fiber or stone, may be used to anchor the roots. These hydroponic mediums are designed to be very porous for excellent retention of air and water that’s necessary for a healthy plant – roots need to breathe too. The tray contains the plants in containers with a growing medium like Rockwool, lava rocks or the like.  A basic system known as ‘Ebb and Flow’ requires the the growing bed to be filled with a nutrient solution by a small pump on a timer to feed and water the plants, the nutrient solution ‘flows’ in. The timer then shuts the pump off and the nutrient solution drains or ‘ebbs’ freely back into the reservoir. Ebb and Flow systems’ are favored because of their low maintenance, high productivity, and ease of use. Ideal not only for the beginner, but for the advanced gardener as well.



There are lots of other systems to consider:

Aeroponics – This method of hydroponics goes without a growing medium, although a small amount may be used to germinate the seed or root a cutting. Plant roots are suspended mid-air inside a chamber kept at a 100% humidity level and fed with a fine spray of nutrient solution. This mid-air feeding allows the roots to absorb much needed oxygen, thereby increasing metabolism and rate of growth reportedly up to 10 times of that in soil and there is nearly no water loss due to evaporation. The mist is created by special nozzles to the root system on a regular basis. The roots are held inside a water proof and light proof container which helps create a high humidity area.

Continuous flow / Top feed system – This is the system you often see pictures of. Using a 2″ or 4″ PVC tube with holes cut into the top at regular intervals for the plants to sit in a holder or pot. The nutrients are continuously fed down the PVC pipe over the root system.

Deep Water Culture (DWC) + Recirculating direct water culture systems (also known as RDWC) + BubblePonics – This is a simple yet effective way to grow, it is similar to the mist Aeroponics system in some ways. However the concept is to submerge the plants roots in the nutrient system, now without air they would die, so you add an air rock like used fish tanks. If you pump significant air through the system the bubbles maintain oxygen to the roots and they grow really well.

Drip Irrigation – A great way to save water and nutes. Used throughout large outdoor farming systems to cut down on waste, small droppers are placed right next to the stem or roots of the marijuana in their pots within the medium. Small drops of the nutrient system will drip out regularly to feed the plant. Very low evaporation and good for stealth grows too because it is silent.

Ebb and Flow – As discussed above the nutrient solution floods a tray situated above the reservoir and then ebbs back into the reservoir in the process feeding the plants with their roots situated to the tray.

Nutrient Film Technique (NFT) – Similar to the Ebb and Flow technique but it is more circular. The tray above the reservoir is tilted and the nutrients fed in from the top and let to drain in a thin film down the tray back into the reservoir, it lets roots feed and have access to air.

Wick system – An easy system where by your marijuana is usually situated in pots, which can have a soil medium, there are thick ‘wicks’ usually of cotton that connect the pots aggregate with their roots with the reservoir below. The nutrients solution is constantly sucked up by the plants when they are dry through capillary action.

Sea of Green (SoG) – This is  Dutch method for growing rather than a hydroponic method. Read all Sea of Green here.

Screen of Green (Screen of Green) – Very similar tot he Sea of Green system but involves a screen situated above the marijuana heads, read more above Sea of Green.

Sea of Green (SOG) and Screen of Green SCOG –  These growing systems are used more by commercial operations where speed and yields are paramount but can be used in smaller home grows. The equipment is different and you need cannabis strains that are capable of flowering after a short vegetation period, read more. If you would rather buy a ready built grow room rather than grab all the gear from the hardware store (they will know what you are making), it may cost a little more but all parts will be included and you will save time by getting everything at once. More about hydroponic grow systems.


Marijuana lighting

Since modern hydroponics began people have used high intensity discharge (HID) lights including Metal Halide (MH) or High Pressure Sodium (HPS) to grow marijuana and more recently with great success, LED grow lights. Metal halide light is close to regular room light or compact fluorescent light CFL and is more abundant in the blue and green spectrum’s which is best for vegetative growth. While high pressure sodium HPS offer light in the orange, amber and red end of the spectrum which is best for flowering stage (later) growth. Growers often use these two lights in tandem, MH for vegging and HPS for flowering or both at the same time. Marijuana grows well from 420 through 730 nanometres which can be covered in this method. HID lamps like the MH and HPS offer a lot of light but just as much wasted energy is emitted as heat. You will need to manage that heat with a good ventilation system. HIDs also require a ballast to operate so make sure you buy one of them. Expect to pay about $250 for a 600W HPS/MH digital ballast, bulb and reflector combo.

Full spectrum LED grow lights are what the pros have turned too now, we know some of the large greenhouses (think big name seed companies) in the Netherlands have turned too as they offer far more control, lower electricity costs while heat and space issues are decreased. Why are LEDs now a good option? The cost of LEDs, their power and the color they produce (spectrum) is tuned perfectly for marijuana growing. LED grow lights, in particular full spectrum LED grow lights, number of advantages over HIDs such as covering the full grow spectrum from seedling, vegetative and flowering stages, run on approximately half the electricity and have bulb lives of around 50,000 to 60,000 hours! A 1000W HPS is the equivalent to approximately 500W LED (true draw). Good LEDs run cool, have no fans or excellent silent fans and emit very little heat – and do not require a ballast. LED grow lights are a great solution to the old HIDs. Much more on grow lighting.

Marijuana Lighting Guide

Marijuana Lighting Guide


Marijuana growing seeds or clones

If you know someone who grows, ask them for a few clones. If you don’t have access to clones you will have to buy marijuana seeds. If you don’t already have some, you can ask you friends to save you seeds out of any good weed they may come across. If you need seeds we totally recommend reading this cannabis seeds guide.



Germinate the marijuana seeds

Set up your hydroponic garden before you germinate the seeds. Make sure everything works fine. If you are using clones, skip this section. There are various types of media available to grow in. Rockwool is one, but there are many others. Media simply means the substance that the roots grow in. Since you aren’t using soil in a hydroponic garden, you need a substitute. The media will provide no nutrition; it is just a support for the roots. All nutrition comes from the hydroponic solution. The standard thing to do is use a Rockwool cube to start the seed on and surround it with whatever growing media you like to use. Keep the Rockwool cube so that the bottom 70% or so is submerged when the water is at its maximum, but keep the top part above the water so that the seed is never submerged. After the seeds have germinated and the root is about a quarter of an inch long, place the seed, root down, on your grow cube or media in your hydroponic cups.


Vegetative marijuana growth

The first phase of marijuana growth is called the vegetative phase. If you plan on using LED, MH or HPS right away, Start with about 20 inches or more above the top of the plant (less for LEDs) and lower the light an inch or so daily until you think the height is right. Too close and the plants will dry and turn brown. Too far and the plants grow too tall as they stretch to get closer to their light source. That is a waste of space. Start high and lower the light an inch or two daily until you think the height is right and the light emitted is being caught well by the plants. During the first stage of growth, the vegetative stage, keep the light on 18 to 24 hours a day minimum. The longer it is on, the faster the plants will grow, but the higher your electricity bill will be. More on marijuana vegetative growth. More on marijuana vegetative growth.


Marijuana flowering

Flowering is the phase of marijuana growth that produces the most THC, CBN and CBD; these are the active ingredients that produce a high when the female buds are smoked. Once flowering begins, the height of the plants will taper off as the plant energy is used in the flowering process itself. You can start flowering when the plants are a minimum of about 6 inches high and have at least 4 sets of leaves. This will take 2 weeks to a month of vegetative growth in most hydroponic gardens. When you want to start flowering cut the light back to 12 hours a day. If you start the flowering when the plant is very small say 6 inches the height of the plant will continue to increase for about two to four weeks after flowering has been started, after that all the plants energy will be used for flower production. If you start the flowering when the plant is a bit more mature it will start in around 10 days. Limiting the height of a marijuana plant has always been a difficult task, so one easy method is to raise the height of the light as the plant grows. There are methods of limiting the height of a plant, but none of them are really easy. We recommend one of the Marijuana Growers Guide which has the most comprehensive descriptions I have seen on limiting the height of weed. The flowering cycle lasts about two months, sometimes a little longer, depending on the type of seed. So the total length of time to raise a crop should be 3 to 4 months in a hydroponic garden but much less if you use the Sea of Green or Screen of Green methods. During flowering the dark period must be perfectly dark. No room light, sun light, or any other light should reach the plant in the 12 hours of darkness that the plant must get everyday. The strongest light that should reach the plant during flowering would equal that of moonlight. Stronger light than this will delay flowering, and if it continues there is a chance that the plant will not flower, but stay in the vegetative phase. You will know the plants are flowering when you see what look like little white hairs developing at bud sites. They should be visible after about 10 to 14 days of the flowering light cycle. This is when you need to remove the male plants, not required if you have female clones. These pistils will eventually be the red or white hairs that you see turn into nice big buds. More about marijuana flowering and sexing.

Harvesting, curing and storing marijuana – no smell

We have a great page all about harvesting your marijuana! If your weed is going to be stored for more than a year it should be wrapped in an air tight container and be stored somewhere that is dark and cool. A freezer is best, but a fridge, basement, closet, or something similar will do. Dry it first if you grow your own, or if the stuff you have is very moist. And remember that light, air and heat are the things to avoid. If you are looking to grow and smoke marijuana of course this will produce odors. Sometimes they can be strong enough to attract attention. If you would like to eliminate the smell from growing and/or smoking marijuana the best thing to do is build an ozone generator. More detail on odour control.

BIG yield seeds, Autos, Fems and great service we always use Paradise SeedsGreen House Seeds, SeedsMan, Marijuana-Seeds.nl, and recommend talking with the grow gurus at Dealzer – they will sort you.

“The best marijuana growing guide we have ever seen online in our 19 years. Save $10 today use code STICKY420 – Click here

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84 thoughts on “Hydroponic Marijuana Grow Guide

  1. bert says:

    Can you please tell me if i am leaving my nutrients on to long during the veg stage of growth eg 18hrs is this too wet?

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  2. Nicholas says:

    What is the perfect ppm & ph for aeroponic indoor grow. What nutrients are the best to use for aeroponic indoor grow. What auto flowering seeds with highest thc is best for indoor aeroponic system. Is it best to use 18 on & 6 off with led lights for aeroponic indoor grow. Thanks for your expertise regarding my questions.

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    Rating: -1 (from 1 vote)
  3. Gary says:

    Is it not harmful to cut the roots of the marijuana if they are too long? Are the roots not malleable enough to bend or somehow move them so they can stay long. It seems like cutting them would be destructive or cause the plant to not get as much nutrients

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  4. Gary says:

    Wow! A Great read, lots of great information. Thanks for sharing!

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    Rating: +2 (from 2 votes)
  5. Jacob Zuma says:

    Hello Friends
    All the way from sunny hot Durban. Yes same place where the poison comes from.
    Thought I would tell you what its like here.
    If you drop the seeds onto the earth they will grow in front of your eyes! Two to three meters high if nothing tries to eat the plants.
    No need for hydro here the stuff grows wild on almost every open piece of ground. Still its illegal! Its like saying as from tomorrow milk is illegal. The prisons here are full of offenders charged with possession of! Still mother nature has a funny way of winning everything in the end.
    Good luck with your hydroponic systems. I am building a monster system but it to grow vegetables.

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    Rating: +4 (from 4 votes)
  6. Smokee-bong-420 says:

    Hey guys I’m new to his just started to grow a couple plants the about 4 to 5 months I just started to do my flowering stage there about 3 feet tall and really bushy I’m just wondering how long dose it take for there first bloom?

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    • ishi says:

      Hi anyone used an IWS system? Its a flood and drain system.i have read loads of good reviews however im strugling to get even an “ok” result..i have used coco and soil and coco was awesome..but this iws not happening.using canna full range canna aqua ph n ec in check.ph between 5.2 max 6.2 according to canna feed n ec at max 1.6-1.8

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  7. valiant says:

    i have a 6′ high by 2’7″ wide by 12′ long space. i was wondering how many plants should i plant and what lighting should i use? i am a first time grower and any tips on any of the process will help greatly. thanks.

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  8. Sandy says:

    Marijuana is a gift from GOD, get the government off of it. Stop cutting down trees for paper and stop sucking the earth dry for fuel. Marijuana can provide all that and it has a ZERO death rate. Peanuts kill 100 people a year, and they’re legal.
    Call Congress and Senate – 202-224-3121 9 a.m. to 5 p.m., Monday thru Friday. Share this number with your friends and family. Help me make the noise to make it happen.

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    Rating: +3 (from 3 votes)
    • Regina says:

      Go on Sandy! If enough people stand up and be counted, we can make change happen!

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      Rating: +4 (from 4 votes)
  9. kellsie green says:

    Ok stupid questions but I am new to this. What seeds do will specifically work with the hydroponics grow cabinets? I am going to buy 2 of them so if the bottom holds 60 babies should I buy 60 seeds or just clone 1 seed? Please leave a few comments with a few pointer as if I had seeds and 2 grow boxes right in front of me now. Just the basics help me out here.

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    • Jamal says:

      All seeds will work Kellsie. It might take a while to build up to 60 plants though. Buying 60 good quality seeds will be expensive. Go for around 10, grow them out, remove the males if necessary (if you buy regular and not feminized).
      Now, select the best female, give her a while to get lots of branches (try lots of topping and pruning) and start taking clones. As she gets bigger you will be able to take more and more clones. Hope this helps.

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    • Lynx says:

      Not all seeds are gonna grow, i just started growing hydroponically, and realized that i drastically undercalculated the hydro ponic systems abilities, we now have 21 sprouts, but besides that, i’d say start with a good 5 seeds, 4 will most likely sprout, those four should be your mother plants and clone off of them after you have determined their sex of course, you want females, look for tiny white strand at the notch (pistils) hope this helps -L

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  10. pete says:

    It has been a month I put a seed with root in my cube in my hydroponics set up now it grew say 5 inchs and only has two of the vegge leaves.Now is there something wrong

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    • Lynx says:

      Check your nutrient solution or pH. May be something wrong in it thats slowling down growth i had 5″ plants in 3 days

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