Fertilizers & Supplements

What are the best nutrients for growing cannabis? There are many nutrient lines and supplements available on the market, some are better than others.  It can be confusing to know which are the best nutrients for cannabis grows and whether the expensive supplements are worth your money. Here we provide our recommendations for what you should look for in choosing nutrient lines and why you should use certain supplements. We recommend the products that we actually use in our cannabis grows.

Fertilizers & Supplements

Base Nutrients

Base nutrients are the foundation of plant nutrition. You want stable nutrients that are well balanced and do not require regular flushing. There are several good nutrient lines, but always check their recommended feeding schedules. Avoid lines that call for high EC and/or regular flushing. 

General Hydroponics Flora Trio
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We use and recommend the General Hydroponics Flora Trio. They are good well balanced nutrients that are perfectly suited to growing cannabis in coco.

Note: General Hydroponics Europe is different in a few respects. They offer both hard and soft water versions of Flora Micro. Always get the soft water version when growing in coco because the hard water version does not have adequate Ca and Mg. The soft water version is linked for the UK.

Cal-Mag Supplement

This is an absolute requirement for both buffering coco and mixing with nutrient solutions. 

General Hydroponics CaliMagic
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You should use the Cal/Mag supplement from the same nutrient supplier as your base nutrients. If your nutrient supplier does not offer a Cal/Mag supplement then they are not expecting their products to be used in coco.

Silicon

Silicon offers significant benefits to cannabis plants. It is not included in base nutrients and it does not occur naturally in coco. We highly recommend using a Silicon Supplement. If you can afford only one supplement after the base nutrients and Cal-Mag, it should be Silicon.

General Hydroponics Armor SI 
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Silicon is unlikely to create adverse reactions with other nutrients, so you do not need to get it from the same supplier as your Base Nutrients. It will significantly raise the pH of your nutrient solution. Be careful when handling as it is very alkaline.

Bloom Booster

During the flowering stage, cannabis plants benefit from much higher levels of potassium (K) and phosphorous (P) and lower levels of nitrogen (N). The Base Nutrients on their own cannot create solutions with high enough ratios of P and K to N. Bloom Boosters work with the base nutrients and raise the levels of P and K. Bloom Boosters encourage flowering, promote the production of essential oils, and improve yield and quality.

General Hydroponics Liquid Kool Bloom
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I use and recommend Liquid KoolBloom. Be careful with dosing as koolbloom has a very powerful impact on EC. Unfortunately, I have not found a suitable substitute in the UK market and would advise to go without rather than crossing nutrient lines.

Humic Acids

Humic acids are soluble components of soil organic matter, which play an important role in plant nutrition. They have been shown to significantly improve nutrient absorption during fertigation. Coco does not provide any soluble organic matter, so to get the benefits, humic acid must be added as a supplement.

General Hydroponics Diamond Nectar
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We use and recommend General Hydroponics Diamond Nectar. In the UK, the comparable product which we linked is "Diamond Black".

Root Enhancer

Root enhancers help promote root development and branching.

General Hydroponics RapidStart
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Rapidstart is pretty expensive so you can skip it if you are on a tight budget, but it really does help with the development of a healthy root mass. Be sure to keep the plastic stopper that comes in the bottle and reuse it every time to ensure a tight seal.

Wetting Agent/Surfacant

Wetting agents reduce the surface tension of the water. In coco, this is important to promote the lateral movement of water in the media.

RAW Yucca Powder
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Since SM-90 is no longer available, I use RAW yucca powder. Yucca is an excellent wetting agent and there is evidence that it brings other benefits to the plant such as improved ability to handle climate changes and pathogen resistance.

Doses are very small! I use 1/8 tsp per 5 gallons. I recommend measuring 1/8 tsp and dividing it into 5 piles. Once you get this sense of how much you need you can just eyeball a pinch. The dose doesn't have to be super precise, but it should be reasonably close.

Anti-Bacterial

If you are running an Auto-Watering System with a reservoir then you will need an additional product to help control anaerobic bacteria. There are two ways to handle this. You can go the sterile route and add Hydrogen Peroxide (H2O2) to the nutrient solution or you can add beneficial bacteria which will out-compete the bad bacteria. Both paths are viable strategies to limit anaerobic bacterial growth in your reservoir.

Hydrogen Peroxide (Food Grade)
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If you use H2O2 you should get food grade H2O2. Food grade is important because lower grades, like pharmaceutical H2O2, contain stabilizers. Only food grade is recommended to use in the nutrient solution.

Full strength food grade H2O2 is usually around 35%. It is often diluted to 12% for safety. If you do get full strength, be sure to handle it with care. Even the diluted 12% products are far stronger than the H2O2 used in First Aid, which is only 3%. With 28-35% H2O2, you use 2.5ml/gal. If you get 12% H2O2, you should double that dose. Add it last, just prior to adding the nutrient solution to the reservoir. It does not affect EC or pH.

We recommend purchasing H2O2 locally rather than online. It is available at better prices in most hydroponic stores.

Botanicare Hydroguard
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Hydroguard is an alternative to Hydrogen Peroxide. Rather than killing all bacteria and creating a sterile reservoir, this product supplies an army of beneficial bacteria which will out-compete the bad bacteria.

Flushing Agent

General Hydroponics Flora Kleen
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Flushing agents dramatically reduce the amount of water needed to flush. They can also help break nutrient lock out with a simple rinse instead of a full flush. When you run into nutrient problems during the grow, a flushing agent will make the solution quicker and easier for you and the plants.

Mother Plant Fertilizers

The nutritional requirements for mother plants  which are kept for clone production are much different than the requirements of plants that are intended for production. Mother plants benefit from a nutrient balance with lower levels of nitrogen and potassium, which prevents excessive vegetative (leggy) growth and increases the carbon to nitrogen ratio. This nutrient balance allows plants to store more carbohydrates in leaves and stems, which aid in the development of roots during the cloning process. In contrast, if too much nitrogen is used on mother plants, the plants will grow quickly reducing these stores of carbohydrates and producing thin and weak cell walls.

Hydrodynamics Two-Part Mother Plant Fertilizer
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If you are doing clones on a regular basis, we recommend Hydrodynamics two-part Mother Plant Fertilizer. It is specially made for mother plants and provides low nitrogen and potassium and high phosphorus and calcium. This nutrient element ratio promotes high carbohydrate stores and healthy cell walls.

Measuring Nutrients

10ml Oral Syringes
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I honestly believe that there is no better way to measure and mix nutrients than with using small oral syringes. I assign one syringe to each nutrient product and I Velcro the syringes directly to the bottles. These syringes measure in milliliters and teaspoons and it is easy to measure fractions of a milliliter. The US and UK sets comes with 10 syringes. The Canadian options are a little odd, but the best deal is an 8-pack of curved tip syringes, which is what we linked. For any grower who is mixing nutes, these are a must buy!

pH & EC/PPM Tools

pH Control Kit

This is an absolute necessity! You need to have a way to adjust the pH of your nutrient solution. We recommend that you use a product engineered for this task because they allow significant pH adjustment with very low doses and have minor impact on the EC of the nutrient solution.

General Hydroponics pH Control Kit 
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For the US and Canada we have linked the General Hydroponics pH Control Kit. It comes with both pH up and down. It also includes a color test kit for measuring pH. This is all you need to start managing the pH of your nutrient solution. We recommend using a pH meter (see below) instead of the color test but having the color test is great for periodic verification. The kit linked in the UK is the best available option.

pH Meter

The technology involved in measuring pH is sensitive and sophisticated. There are numerous cheap pH meters on the market, but these are shortlived and unreliable. You do not need the most expensive models, but it is worth investing in a quality pH meter. 

Apera Instruments pH20
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Dr Photon and I both use and recommend this Apera Instruments pH meter. It is easy to use, reliable and accurate. I have owned it for a year now and it has proven very consistent and rarely needs calibration. It also comes with small jars of calibration fluid, rather than powder. It is a great balance of quality and price for a pH meter for home cannabis grows!

pH Calibration Solution
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All pH meters require calibration eventually. The Apera unit that we recommend above comes with small bottles of calibration fluid that will get you through a grow or more. Other meters come with powders which are very difficult to mix. Rather than using the powders or using an inaccurate meter, get some pH calibration Fluid and learn how to keep your meter tuned up.

Electrical Conductivity (EC)

Measuring Electrical Conductivity (EC) is absolutely critical to managing your fertigation strategy and nutrient solution strength. The technology involved in measuring EC is rather simple which means that you do not need to invest in an expensive meter. However, if you use one of these meters, the water should be measured at about the same temperature that it is applied to the plants (about 68f/20c).

EC/PPM meter
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The meter that I use is pictured and linked for the US amazon. I have verified its accuracy against other meters and it has served me well for more than 5 grows. The UK and Canadian options are similar models sold under different brands.

About Our Product Recommendations

At Coco for Cannabis, our mission is to help growers maximize the success of their cannabis crops by providing scientifically accurate information and sharing proven growing practices.

The products that we recommend are the actual products that we chose to purchase and use ourselves. In a few cases, we recommend products that we would buy if we needed them. We do not accept advertising and will not recommend any product that we would not buy for ourselves. We offer this guide as a resource to growers.

We may receive a referral when you purchase products through this page. This is the main revenue stream that keeps Coco for Cannabis up and running! When you click through our links and make purchases you are supporting our work! As an Amazon Associate, we earn from qualifying purchases.

Whether we receive a referral does not influence our recommendations. For example, when products are cheaper to buy locally, we’ll tell you that rather than just recommend a more expensive online option.

Disclaimer:

The information on cocoforcannabis.com should not be considered as financial, legal, or medical advice. You are responsible for knowing and following the local laws that pertain to cannabis cultivation, possession, and use. Decisions to grow cannabis should be made in consultation with a lawyer or qualified legal advisor. Decisions to use cannabis should be made in consultation with your doctor or medical professional.