As the grower begins to experiment with soil types and mixing them they may begin to look at alternative growing mediums such as rockwool or Clay pebbles. These are mostly artificial grow mediums designed to contain all the plants mineral needs and allow air to get the roots to promote good growth.

Diy Hydroponics Cannabis
Figure 9.1 - This is a picture of rockwool in various forms. You can see slabs and cubes in this picture. 'Grow Dan' is a popular brand of rockwool.

In the early days of experimenting with artificial grow mediums inventors found that plants just needed a suitable material that holds minerals, performs some form of drainage and allows air to get to the roots. If they could invent a non-toxic medium then the plant would surely grow as well as it would in soil. During most investigations they found that the roots did not respond too well to the mediums, but that the plant was receiving nutrition in every aspect when the nutrients were added to the artificial medium by hand. To solve this problem the inventors looked back into the history of growing. They found that many Ancient Civilizations where growing their plants directly in running streams. A light reed or bush was used to keep the plants stems above the rushing water. Of course the inventors knew that only certain types of plants could be grown this way. Then someone had the bright idea of creating a small unit that held water and had the medium and plant set-up in such away that the medium would support the plant above the tank that would feed water to the roots once they grew out of the medium.

Figure 9.2 - Rockwool cubes are excellent for cloning.

Figure 9.2 - Rockwool cubes are excellent for cloning.

Figure 9.3 - This is the underside of a hydroponics system. Notice the root masses hanging down like fine clear strands. Root masses can really grow long in hydroponics systems. This image is by Shipperke.

The method is called hydroponics and is a very successful way of growing marijuana if you are looking for large bud quantities, or bud all year long.

Hydroponics is the technique of growing plants without soil, but rather in beds of sand, gravel, or artificial mediums that are flooded with a nutrient solution.

Basically a simple hydroponics system consists of a pot, a reservoir, a grow medium, a pump and a set of growth nutrients. The system itself has a top layer and a lower layer, The top layer holds the grow medium and the bottom layer holds the water with added nutrients. The plant is grown in the medium where it will develop a stem and a set of roots. The roots will grow through the medium and down into the nutrient solution. Water and nutrients are pumped into the lower portion of the tank through a reservoir at certain timed intervals. The plants drink the solution down and thus exposes their roots to the air more. If this it timed correctly and the growing solution is maintained the plants will flourish! This is because the plant can devote more of its energy into upper-body growth rather than putting that energy into roots searching for water and air. Now having said this, hydroponically grown plants produce massive root clusters and I mean a big mass of roots.

One can easily pick up a 2-gallon bucket full of root growth from a single plant! This is because roots thrive in hydroponics systems. Hydroponics has become a fast growing trend in cannabis cultivation. It does require a certain degree of maintenance, but the results are sometimes incredible. On the other hand if a hydroponics system is not well maintained the whole unit may fail and kill your plants very quickly. This is the biggest problem that the hydroponics grower has to contend with.

Hydroponics, when done correctly, can produce a flowering plant up to 3/4 the normal time that it would take with a soil grow. That is right! Hydroponics can grow bigger and better buds in 3/4 the time it takes to grow the same strain in soil.


There are many hydroponics systems out there but here are ones that are most commonly used.

- Nutrient Film Technique - NFT

- Drip Irrigation System

- Aeroponics

- Automatic hydroponics Pots

- Manual hydroponics Pots

Figure 9.4 - This is a picture of an NFT system.

An NFT system is an all-in-one system. In other words the reservoir which holds the pump and nutrient solution is contained in the same system. These systems are generally very flat and long. There is a constant flow of nutrients to the roots and back to the reservoir.

Figure 9.5 - This is a professional reservoir unit. It is light tight and contains perforations for pump attachments.

Figure 9.5 - This is a professional reservoir unit. It is light tight and contains perforations for pump attachments.

Figure 9.6 - This is a popular Ebb and Flow system on the market today.

Figure 9.6 - This is a popular Ebb and Flow system on the market today.

An Ebb and Flow is another all in one system that is recognized by its depth. The grow medium is located above the reservoir which pumps the nutrients and water to the roots at a set time and rate. This means that during the day the plant will go through spells of dryness. The nutrient solution is pumped into the medium and is slowly drained back into the reservoir again. The whole unit recycles the nutrient solution at timed intervals.


The Drip Irrigation System is another all in one system that feeds the plants individually. The plants are located in separate chambers and the nutrients are fed to the medium by a small dripper. The solution is drained through much like an Ebb/Flow system.



Aeroponic Irrigation System

Figure 9.7- This is an example of an aeroponics system.

Figure 9.7- This is an example of an aeroponics system.

Figure 9.8 - Aeroponics can be classified as a branch of hydroponics, but in recent years it has become something of a method in a field of it's own.

These systems are generally expensive and are used by professional growers. The unit itself can be recognized straight away by its design. The plants are grown in a medium that is placed into slots along a lengthy tube. The tubes can run anywhere from 1 meter to 20 meters in length. Inside the tube are nozzles which mist down the roots of each plant with grow nutrients. The reservoir, which contains nutrients, is kept outside of the tube in a tank. The nutrients are pumped from the tank to the nozzles and then the remaining solution that drips from the plants is drained into another tank that is normally checked before being reused again.

Figure 9.9 - An Aeroponics unit in use by Taffy


Figure 9.9 - An Aeroponics unit in use by Taffy


Figure 9.10 - This is a complete aerokit with over 20 plants. Picture by Taffy Lewis.


Figure 9.11 - This is an example of an automatic and manual pot system.

Figure 9.11 - This is an example of an automatic and manual pot system.

These are pots that are used for growing one plant at a time. In each pot a pump delivers the nutrients (or they are manually fed by hand), into the bottom of the pot until the nutrients reach the roots. The roots then suck up as much as they can until they are dry. Once the roots are exposed the pot is fed with more nutrient solution again. These units are good for the grower who wishes to grow big bushy cannabis plants in a simple stand-alone unit.


This is the most important part of your hydroponics set-up. Your mix and the choice of nutrients will depend on whether your plant will die, grow, grow big, or grow very very big.

Nutrient solutions basically come in a number of different forms. It is vital to check that the solution you use is the best for your type of plant. Some solutions are for soil and can only be used with soil. They contain the wrong elements for hydroponics use. There are soil-based supplements/fertilizers and then there are hydroponics nutrients.

Most hydroponics nutrient solutions are complete nutrient solutions. They provide every element and compound needed for proper plant growth. Because of this hydroponics nutrients are a bit steep in price. Always spend your money on the correct nutrients because any short cuts will lead to failure and kill your plant.

Single Packs:

If all the nutrients are contained in a single pack there is a chance that the elements may combine and precipitate in the pack. This may cause the solution to become unbalanced and is then rendered useless to you and your plants. Keeping this in mind, get a complete nutrient solution that is contained in several bottles called ATwin' or ^Triple packs'.

One brand name called Formulex has managed to hold all the elements in a single pack using certain chemicals to prevent precipitation. This pack is very good for starting clones or seeds in a rockwool SBS tray. Formulex can be used in soil grows also.

Figure 9.12 - Formulex Twin / Triple Packs:

Figure 9.13 - This is an example of triple pack nutrients.

Figure 9.13 - This is an example of triple pack nutrients.

For best results the hydroponics grower should consider a Twin or even a Triple pack.

Basically the chemicals are held in different packs to prevent precipitation. Optimum, Power Gro, Ionic, and General hydroponics Flora Series are the most common multi part nutrient solutions. The most popular one with cannabis cultivation is the G.H. Flora Series, a 3-part system, Gro, Micro, and Bloom. An experienced grower can adjust these nutrients to get optimum performance from their plants.

These packs have instructions on the bottles explaining how to mix down the nutrients into water, and can be broken down and mixed weaker or stronger to the grower's needs.


Depending on what set-up you are using, you may find that your solution goes through a system that uses the nutrients in the reservoir over and over. As the plant extracts the nutrients and minerals from the solution it will become depleted of its resources over time. For this reason we must understand how to monitor our nutrients. In today's world monitoring systems are a bit expensive. If you have a ppm reader (TDS meter, Total Dissolved

Solids) you can understand how much of your nutrients have been used up and how much more you need to add to reach the optimal nutrient level. All reservoirs will become unbalanced and need replenishing. As a general rule, an initial amount is used to fill the reservoir. As the plants use up the solution, we top up the reservoir to maintain the initial level.

If you start with 10 gallons of solution then we need to top up to that total of 10 gallons every few days.

Figure 9.14 - Ppm reader (TDS meter).

If you do not have a reader you can still grow a good crop, but it takes practice to get it right. If a cannabis hydroponics grower does not have a ppm reader, then they tend to replace the reservoir more often instead of topping it up. That way the grower is certain that the new solution will contain everything the plant needs. If you have a ppm reader then you only need to top off the reservoir as needed. PPM (parts per millionth) readers can be expensive, but over time they will help you save money on the cost of hydroponics nutrients.


There are many hydroponics mediums to use that your plant will take root in. Rockwool appears to be the most popular and comes in either slabs or cubes. These cubes vary in sizes from 1" to 6" cubes. The slabs can be cut to suite the shape of your pot or container.


Many growers like to use the cubes for seed germination and for rooting cuttings. This seems to be the easiest to use. Many growers claim that rockwool should be pre soaked for 24 hrs in water with a pH level of 5.6. This is to stabilize the pH level of the rockwool.

How to make up nutrient solutions:

Always follow the very simple instructions on the products. All you need is a container to make up the nutrients in and the nutrients themselves. Each of the packs should have A, B, and C written on them. The mixture is usually 3.5mls of A and B and C per litre of water. This is called a 100% strength mixture if you follow the guidelines as stated exactly on the label.

Hydroponics pH:

After you have mixed up your nutrient solution you will want to take a pH reading of it. If you have any problems, just like in soil growing, you will need to adjust your pH level. Now, you do not use the same method to adjust pH levels as described in the soil chapter. For hydroponics you need to buy a pH Up and pH Down adjusting solutions. These are cheap and can be added to your solution to balance the pH level.


Cannabis plants in a soil systems like a pH of 7, but in hydroponics systems they like a pH of 5.2 to 6.3. You will discover it is easier to maintain a pH range and not a set level.

Figure 9.15 pH up and pH down products for hydroponics use.

Figure 9.15 pH up and pH down products for hydroponics use.

Always check your hydroponics pH level as often as you can. pH can slip up and down very quickly in hydroponics systems.


Alga is part of a large group of non-vascular mainly aquatic cryptogams capable of photosynthesis.

Always keep your container away from exposure to direct light, as alga will grow in the container if you do not. This seems to be something of a problem because we grow plants under lights and we may have a system that has to be sitting near the light so the plants can grow properly. Most hydroponics systems have been manufactured Alight tight' to eliminate this problem. If you built your own system then you may want to keep your solution sealed from the light by using thick black PVC tape to cover the lid and the entire reservoir. This will help prevent alga from growing in your system.

If you do have alga growth then you need to clean your system out. Wash the unit and replace the nutrient solution with a fresh mix.

Also try to find the source of the light leak and patch it up. Using a thick black garbage bag works well to keep the light out.

Grow and Bloom:

Some of the double packs come in two different sets - Grow and Bloom. Basically the Grow solution is used during the plants vegetative stage and the Bloom is used during the flowering stage. The Bloom formulas contain more Phosphorus and Potassium and less Nitrogen.

Other packs have a complete all in one function, but they are lacking some additional extras.

Cannabis may find a lot of the nutrients that are mixed full strength to be too strong and it will burn them. It is recommended that when using any hydroponics formulations with cannabis that you do so in MODERATION for your first grow. Many cannabis growers have bought these products with anticipation of producing great buds only to get great plant burns instead. It is best to start off with 30% strength at first and then increase if needed.


Marijuana cultivators have found that full strength nutrient solutions are not a good thing. In fact even medium strength formulas have the power to burn your plants. Consult the information on the packs, but in general 3.5 mls of A and B and C per litre is usually called 100% strength. The same amount mixed with 2 litres of water is 50% strength. Marijuana can grow very well between 30% and 50%. Never go full strength with your nutrients if this is your first time. Try 30% for the first attempt and see how your plants do. You will be surprised at how rich a bud content you will produce with this amount of nutrients. The most common problem associated with hydroponics is plant burns. I have rarely heard of someone under-feeding his or her plants in a hydro system. I have heard plenty of reports about overfeeding plants in hydro systems. Over time you will get to know your strain and what it likes. The better you know your strain the better you will be able to control your feeding amounts.


If you have scales in your bucket or what looks like kettle rust then you have not been maintaining your pH level. Scale is caused by very acidic pH levels. Your local water company will provide you with a read out of your water. You can buy nutrient products to use with hard water. If this problem persists just drain and clean your reservoir and mix a new batch of nutrients to the correct pH level. Some use a Reverse Osmosis water filtering system to clean their tap water. Distilled water has a stable pH level of 7.0.


This is easy and not so easy. Beginners rely on a ppm meter, but a veteran grower learns to read the plant. The plant will tell you if is getting enough or too much or too little. It takes a few grows to learn to read the plant but you can do it with experience. The plant may have drunk all the nutrients up or just some of them. Some nutrients are taken up by the plant and stored within the plant until it needs more. A top up can be done if you do not want to change the reservoir totally. If you do not have a PPM meter to calculate this accurately, simply write down your nutrients mix ratio from day 1. Let's say we used 3.5 ml of A and B and C in a 1 litre drum. Now the plant has drunk 1/2 a litre, now all you need to do is make another litre of 3.5ml mix in another container and add 1/2 of it to the reservoir. This is one simple way of doing it, but you are left with a half litre of solution, so do your math and make a mixing chart so you can mix up different amounts as needed. Local grow shops will help you most of the time with any questions that you might have about their products.


Growing in hydroponics is not rocket science. It is a simple process which can vary from system to system depending on what kind of a set-up you choose. Most of the nutrient mixes are explained extremely well on the packs. If you follow their instructions and remember that Cannabis only needs 30%-50% strength nutrients then you will do just fine.

Over the years Cannabis cultivators have decided to try and beat the system by building their own systems. There are over 100 different types of systems that can be made by hand at home. Out of these 100, 15 have proven to be useful for cannabis. One of the more famous simplest systems is DWC, Deep Water Culture, a.k.a "The Bubbler". This system is very cheap to put together and yet still provides excellent growth rates. There is nothing like it for the price. The bubbler is a rewarding way to grow.



Figure 9.16 - A picture of a Bubbler by Strawdog.

Basically the bubbler is just a bucket with a lid and pump. But the set-up is so extraordinary that it simply zings the plant into life. This method can grow a plant from 5 ft. to 8 ft. (if not more), with plenty of fresh buds as long as it maintained and managed well by you, the grower.

Here is a list of what to you need to build the bubbler.

The Bubble Bucket:

(1) Get two 5-Gallon buckets with lids. (Wash it out with bleach)

(3) Cut a hole in lid of bucket so the net pot sits in neatly all the way down.

(4) Cut a hole in the lid about 2cm in diameter near the rim (the pump hose goes in here).

(5) Use Black gaffer tape to wrap the pot so it is light proof. (If light gets in alga will develop in the water. This is not good.) Wrap the lid as well.

(6) Get a fish-tank pump and air-stone.

(7) Get your medium together - rockwool, clay pebbles etc.

(8) Get the Nutrients and Mixes together.

Figure 9.17 - A close-up of the net pot and lid by


Figure 9.17 - A close-up of the net pot and lid by


Simply mix your nutrients together in the second bucket. Set the air-stone in the centre on the bottom of the first bucket and hang the air pump somewhere above the water level on the wall of your grow room. Use the hole in the lid to feed the airline through. Fill the bucket up with the nutrients to a level were the net pot just touches the solution. Turn on your air pump for 24 hours a day. That is it. The pump will send air through the tube to the air-stone and it is released into the water. The air bubbles the solution causing it to splash at the surface wetting the roots and feeding the plant. Check the bubbler everyday to see how much your plant has drunk. Let your roots get air everyday by letting a root zone form. Let the solution level drop an inch below the net pot. The net pot holds the cutting in rockwool and the rockwool is surrounded by the clay pebbles. Do not constantly top up your reservoir, it is sometimes better to let the water level drop 1 gallon and then replace that gallon. Once a root mass has develop the plant will grow like no other.

Figure 9.18 - A close-up of some early roots and underside of the net-pot. Picture by Strawdog.

Basically this set-up is just bubbling the nutrients solution with the pump. The pump sucks in air from the room and this air contains Oxygen that the roots need. As the unit bubbles the roots get air, nutrients and water. The plant loves this and thrives.

When you want to change your mix you may have a spare bucket that is the same shape and size. Simply swap the lid over with the plant, root-mass and air-stone into the new bucket. This is a great little system that comes highly commended.

Growing Soilless

Growing Soilless

This is an easy-to-follow, step-by-step guide to growing organic, healthy vegetable, herbs and house plants without soil. Clearly illustrated with black and white line drawings, the book covers every aspect of home hydroponic gardening.

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