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Hydroponic Nutrients

Marijuana Fertilizers

As well as some trace minerals all plants need three basic macro elements to grow: nitrogen, phosphorous and potassium (N-P-K) and numerous trace elements. Fertilizers contain these macro elements in various quantities and will label them in this order, thus a label that states 10-5-5 will contain 10% nitrogen, 5% phosphorous and 5% potassium. Each of the elements have different properties to offer the plant. Roughly speaking, nitrogen encourages vegetative growth, phosphorous promotes the growth of roots and flowers, and potassium helps with root development and photosynthesis. Consequently a fertilizer high in nitrogen is suitable for vegetative growth and one higher in phosphorous is suitable for flowering. Luckily all of this work has been done for you by the manufacturers. Ideally you will buy your hydroponic nutrients from a hydroponics shop where you will receive good advice. If you buy from a garden centre – think tomatoes!

Macro or Major Nutrients

  • Nitrogen (N)
  • Phosphorus (P)
  • Potassium (K)

Secondary Nutrients

  • Calcium (Ca)
  • Magnesium (Mg)
  • Sulfur (S)
  • Trace Minerals or Micronutrients

Non Essential Additives or Supplements

  • Amino Acids and Vitamins
  • Molasses
  • Humic and Fulvic Acid

Marijuana Fertilizers

  • Pre-Fertilized Soils
  • Quick-Release Fertilizers
  • Time-Release Fertilizers
  • Bone Meal
  • Blood Meal
  • Fish Emulsion
  • Worm Castings
  • Bat Guano
  • Seabird Guano
  • Kelp
  • Carbohydrates

Measuring Instruments

  • pH meter
  • PPM-EC Meter
  • PPM-TDC Meter
  • pH and PPM levels
  • Where can I get them?

The Basics

Macro or major nutrients

Nitrogen (N), phosphorous (P) and potassium (K) are the nutrients your marijuana plants need in the largest quantity to thrive. These are listed on your nutrient package/bottle as N-P-K as a ratio. More detail on N-P-K fertilizer ratio.

Nitrogen (N)

Nitrogen is an essential part of all plant cells and is a building block of proteins and enzymes as well as chlorophyll, the green pigment that gives plants their color and is responsible for photosynthesis.

Phosphorous (P)

Like nitrogen (N), phosphorus (P) is a crucial element in the transformation of solar energy into chemical energy. It is involved in the formation of plant sugars, oils waxes and terpenes, which give marijuana its distinct flavor(s).  It is necessary for plants to mature and for its immune system.

Potassium (K)

This element is necessary for photosynthesis, the formation of flowers and the building of plant proteins.

Secondary nutrients

Note that most nutrients are not usually provided as pure elements, but bound up in compound molecules. This allows the plant to break them down as needed and decreases the risk of toxicity. Next in importance are the elements calcium (Ca), sulfur (S) and magnesium (Mg). Most soils contain enough of these from decomposing organic matter that they need not be added, but must be present in a hydroponic solution. Calcium and Magnesium are sometimes added to soil as lime or as the commercial product, Cal-Mag from Botanicare. Epsom Salt is a good supplement for magnesium and sulfur and is available cheaply from any pharmacy.


Calcium is an essential part of plant cell wall structure, provides for normal transport and retention of other elements as well as strength in the plant.


Magnesium is part of the chlorophyll in all green plants and essential for photosynthesis. It also helps activate many plant enzymes needed for growth.


Sulfur has many functions such as aiding in the production of protein, enzymes and vitamins. It is necessary for healthy root growth and seed production.

Trace elements or micronutrients

In reality these elements are not less important than the others, but growing marijuana only requires very minute amounts to function properly. These include boron (B), copper (Cu), zinc (Zn), iron (Fe), molybdenum (Mo), chloride (Cl) and manganese (Mn). To better understand what to add and when read about nutrient cycle timing.

Non-essential additives or supplements

These are substances that may aid in enhancing growth or blooming, but ones that marijuana makes on its own and does not require external amounts for growth.

Amino acids and vitamins

Some manufacturers add these to make their solutions appear different than rivals with the idea that more stuff is better. While it has been found there is some science behind them, it remains to be proved that these actually increase growth. If you want to experiment with them, do so after you have your grow dialed in with the basics first.


Unsulfured blackstrap molasses is a popular additive because it is cheap, has a high micro-nutrient profile, is high in phosphorous for flowering marijuana (blooming) as well as iron; and is high in carbohydrates.  These sugars do not directly aid your weed, but feed beneficial soil bacteria. The key word here is ‘soil’. Molasses is not to be used in a hydroponic system.

Humic and fulvic acid

Often spoken of as different substances, fulvic acid is a sub-group of humic acid, which is actually a collection of acids from the break-down of humus or similar organic compounds. Fulvic acid, the most ‘plant friendly’ of the humic acid group, is a colloid and as such aids with the transport of nutrients in the plant by making them easier for your weed to absorb nutrients. While such acids are naturally occurring in soil, will the addition of humic acid formulations help with hydroponics or speed up soil grows?

Marijuana fertilizers

You have many different paths to choose from when selecting fertilizers to grow marijuana indoors.

Pre-fertilized soils

While all commercial potting soils have some nutrients, there are many now that contain a full 3-4 months of plant food already integrated. These are perfect for new weed growers and gardeners, just make sure you water regularly. Check out generic gardening mixes such as Miracle Grow or the more marijuana-oriented Fox Farms line.

Quick-release fertilizers

There are too many to list, but all make the nutrients available from days to weeks. These may be added in solution as part of your regular watering or placed dry on top of the soil. Check out Dyna-Grow and Advanced Nutrients.

Time-release fertilizers

These may come as a powder such as Fox Farms’ Marine Cuisine (meal, shrimp meal, seabird guano, and kelp) and American Pride (earthworm castings, bat guano and cottonseed meal). These are mostly, but not completely, organic mixes added to unfertilized soil at about one tablespoon per gallon of soil. More may be added later by putting around the edge of your container and raked in lightly. Do not put near the base of your plant.

Hydroponic Nutrients and Marijuana Fertilizers

Or they may come as capsules of nutrients in semi-permeable spheres such as with Osmocote (12-12-12) or Osmocote Plus for added micro-nutrients.

Bone meal

This organic additive is composed of crushed and ground bones, generally bovine. Low in nitrogen and containing no potassium, its main use is to supply extra phosphorous and calcium.

Blood meal

A slaughterhouse by-product, this dry powder is exceptionally high in nitrogen.

Fish emulsion

This is the liquefied remains of the unused parts of fish from the fishing industry. It has a complete NPK profile along with many micronutrients.

Worm castings

One of the best and safest additives you can put in your soil is worm manure. Worms break down organic matter and deposit it in the soil in a form that is readily available to your plants. Very rich in nutrients yet will not burn plants.

Bat guano

This is mainly bat feces + decomposed bats + cave minerals. There are many different types depending on the species and feeding habits of the bats from which the manure is collected. It is a complete organic NPK food with many trace minerals though somewhat low in potassium.

Hydroponic Nutrients and Marijuana Fertilizers

Seabird guano

Concentrated droppings from gulls are another great complete organic fertilizer source. Higher in nitrogen than bat guano, this is used mainly in the vegetating stage.


Kelp is brown seaweed that contains dozens of minerals and trace elements, vitamins, enzymes, proteins and growth hormones such as auxins, cytokinins and gibberellins that aid cell division growth and flowering. It can be used any time during the growth cycle for better health.


These are non-essential additives that provide fuel to both the marijuana plants and the microbes that break down the soil. Advanced Nutrients Carbo-Load is one such product. It provides both simple and complex carbohydrates plus fulvic acid for better root development. For a much cheaper alternative add one teaspoon of unsulphured molasses per gallon of water.

Measuring instruments

Without knowing exactly what nutrients you are putting into your plants, it is difficult to optimize growth or to diagnose and adjust any nutrient imbalances. Read all about nutrient deficiencies. While you can grow healthy plants without any of these tools, if you are serious about your hobby or commercial enterprise and getting the maximum harvest possible, you will need the following tools:

What are PPM and pH Meters

You've probably scrolled through enough forums by now to make your head spin. Still, there are some questions that remain unanswered, yet they are so basic it would be wrong to begin growing marijuana without these simple answers. If you are serious about growing some good quality marijuana and want to avoid a whole lot of problems with your nutrient solution then you will need to know what your pH is and use a PPM meter to measure the Parts Per Million within your solution. As discussed your nutrient solution will contain Nitrogen (N), Phosphorus (P), Potassium (K) and also chemicals like calcium and smaller trace elements. These elements start their life in rock form; they are then ground down into a power which is soluble in water and makes your nutrient solution. So you use a PPM meter to gauge how many Parts Per Million of each chemical you have in your nutrient solution. You don’t want too many or too little and often you want different amounts of each of the main chemicals as you grow your plants from seedlings through to flowering. If you're using coco, the PPM level is one thing you should definitely keep your eyes on. You see, coco is a blank page, so to speak. It does not provide the plant with any nutrients and that’s why you have to monitor it constantly in order for your plant to grow properly. The pH level is used to determine the acidity of the nutrients/soil/water you are using.

pH meter

The pH meter is a bit different as it measures the acidity of the food that you are about to provide your plants with. It is also used to measure the acidity of the soil or water you grown your plants in. It’s a good thing to use a similar method for measuring as you did with the PPM meter. First you measure the water on its own, and then measure the water with the nutrients. The only difference here is that there is no need to subtract anything because if the total pH level is well balanced, your grow is good to go.

Hydroponic Nutrients and Marijuana Fertilizers

These hand-held digital instruments are a must. By measuring the acidity/alkalinity of your reservoir daily and using pH Up and pH Down solutions, you can adjust your water’s pH to the optimal level. For most strains of hydroponic marijuana the optimal pH level is 6.0 +/-0.2. Going too much outside this range can slow the proper uptake of nutrients or stop growth altogether.

Hydroponic Nutrients and Marijuana Fertilizers

PPM - EC (Electrical Conductivity) meter

This is used for measuring the electrical conductivity of your water. The more dissolved minerals, the higher the conductivity. This is another way to measure for TDS by running a current through the solution. The more dissolved mineral salts, the higher the current. The PPM meter roughly measures how much food there is available. Too little and your plant will grow very slowly; too much and you can shock or kill your plants. While pH requirements stay steady throughout your grow cycle, the PPM requirements change for the different stages. The requirements also vary from strain to strain.

PPM - TDS (Total Dissolved Solids) meter

The PPM meter keeps track of how much food for the plant is in the water itself. For instance, if you want to be really precise about it, the first thing you have to do is to take a water sample you are about to use in your grow and measure the PPM level of it with your PPM meter. Then add the nutrients in the water and measure the PPM level with the added nutrients. In the end you just subtract the standalone PPM water level from the total PPM level with the nutrients mixed in. That way, during the plants growth, you can always tell if there are too many or too little nutrients in the water. This tool will allow you to measure the amount of any inorganic dissolved solids as PPM (parts per million). Pure water is zero PPM.

Hydroponic Nutrients and Marijuana Fertilizers

PPM - EC meter or TDS meter?

Either tool may be used as they are performing a similar measurement. The best one to get is the one used by your nutrient manufacturer as that way you will be in alignment with their measurements. Some of the more expensive units (around $100) measure temperature, PPM, EC and TDs.

Hydroponic Nutrients and Marijuana Fertilizers


pH and PPM levels

Even though marijuana is a pretty resistant plant (it is weed after all) you have to nurture it properly. The amount of love you give to your plant corresponds to the amount of magnificent buds you will receive from it. That is why you have to avoid nutrient disorders. This is best done by keeping your pH and PPM levels ideal. Therefore, be sure to keep your pH level between 5.5 and 6.5 and your PPM level in the range of 900 to 2800. If you keep the condition of your plant within that frame, you'll have no problems

Electron frenzy

The NPK solution will exchange ions and electrons within the chlorophyll and proteins of the plant. These macro and micro elements are what drive their growth and help make the sugars (starch) or energy plants require to grow. Whether you are using your own home grow nutes, or are buying from the big boys like Fox Farm, Advanced or Canna and even though you have followed the instructions on the side of the containers (tablespoons or grams per gallon) you will still want to check nutrient levels to see if are on the right course or in fact want to fine tune your mix, do some trials and compare grows.

Unused salts

You may think that the remaining nutrient solution is the just the same as when you started your ebb and flow, but just less of it in volume, you would be wrong! Each time your solution is used by the plants they take what they want and leave ‘unused salts’ which build up in your solution and change what you are feeding you plants. Change nutrients – Unless you are constantly monitoring and buffering (topping up on specific nutes) then you should look to change your entire solution every two weeks.

Where can I get them?

One of the best meters in the business can be found on Full Bloom Hydroponics website: Be sure to check out the Prestige PH meter and the Prestige PPM meter. They are both waterproof, extremely precise and have low power consumption. Basically, these are ideal and must-have products for a newbie grower. While marijuana can be grown without these tools it is very difficult to tell exactly what is going on or if you are in the optimal zone. This is why it is ALWAYS a good idea to start at half the manufacturer’s recommendation and s-l-o-w-l-y increase the feeding so that you may closely monitor your plants’ response. If you switch hydroponic nutrient vendors, you must also be careful as not all formulations are the same. Similarly, be cautious when trying a new additive. Over-eager growers frequently harm their plants by adding too much. More is not better.

The Basics…

By far the most important thing to do with your nutrients is to follow the manufacturer’s instructions. This is very important. Do not be tempted to exceed them in the hope of growing bigger plants. This does not work. In fact, the biggest cause of plant death is from over feeding. Pay special attention to seedlings and feed them on half dosage until they are strong and well established. Your marijuana nutrient solution should be kept at a suitable and stable temperature range between 68°F and 74°F (20°C – 23.3°C). In cold climates you may want to consider a submersible water heater designed for tropical aquariums. Ideally, you should look to insulate the reservoir so that extreme temperature changes do not create problems or look to have your entire room at around the 72°F to 77°F (22.2°C to 25°C) range. We recommend starting simple with a complete time-release marijuana fertilizer and only begin experimenting with organics after you gain experience growing marijuana indoors. Try not to be overwhelmed by this reference for marijuana nutrients as you need not understand all the internal chemical reactions and metabolisms going on in your weed. Just give it the essentials and your plants will do the work for you! If you plants gets sick try the helpful people at the grow forum.