Best Hydroponic Nutrients
by Growth Stage

My Top Pick

This is my review of the best hydroponic nutrient products in 2021. I have reviewed 15 products from Fox Farm, General Hydroponics, Humboldt Secret Supplies, Zeus and Pluto, Advanced Nutrients, Pure Produce and Element Nutrients to get you as much information as possible with explanation of why something is important and help you choose the right one.

I have selected the General Hydroponics Flora Series primarily because it would require little adjustment in dosing in order to deliver the “expected” typical and generic levels of N-P-K ratio (see later section on “How much to feed the plants”). I want to emphasize here that although the rest of the shortlisted products would also do the job, I find that they would need a little bit more adjustment compared with the General Hydroponics Flora Series. There are of course, specific nutritional needs for different growth stages, plant species or even climatic conditions. So if your plants have specific needs you may need to select a different set of products, such as from Element Nutrients, or Fox Farm.

It is not a straightforward answer as to which one is best, because there is chemistry involved, and there is no one-size-fits all approach. The scientific community has not given one single approach to what is best to feed plants. So the criteria I have used to come up with the shortlist are:

  • How the weekly total N-P-K quantity added to the nutrient solution fits with the typical expectation for:
    • more N in the vegetative stages, more Phosphorus at late vegetative and early blooming stages and more K at late blooming and ripening
    • K being around 50% more than N at the fruiting stages
    • P being lower than N
  • How easy it is (how flexible the product is) to adjust the quantity of each of the N, P or K added to the nutrient solution to fit bespoke needs
  • Availability of secondary macro-nutrients and micro-nutrients in the products
  • Product reviews from users
  • Availability on the marketplace

Parameters that did not influence the review were:

  • The total cumulative N-P-K quantity as per recommended feeding schedule, because the total quantities in absolute terms do not matter. What matters is the ratio of the N-P-K in the different growth stages
  • Price; price did not get in the way of analysing data and reviewing the different traits of each product

All the 5 shortlisted base nutrient products as presented below are very good products, with very good reviews and made from well established companies. I though think that the 3-part products offer the flexibility to adjust dosing to your plants specific needs.

Reviews: the 5 best

I have shortlisted the 5 best hydroponic nutrient products in the table below. I have estimated the total grams of each N, P, K that can be added to the nutrient solution based on the recommended feeding schedules and I have analysed how much of that is given every week from germination to fruit ripening. Where ranges were given for weekly dosing I have used averages. You will see that these 5 products differ in some cases significantly. Not only in the cumulative grams of the N, P, K elements over a feeding schedule of 12 weeks, but also in the relative quantities each week.

General Hydroponics Flora Series

Flora Series from General Hydroponics is my top pick out of the nutrient products I reviewed. It is a liquid 3-part set of products coming in different sizes: pint, quarter and gallon.

I have analyzed how much of the key nutrients is added across a typical 12-week feeding schedule if the recommended by the manufacturer dosing is followed.

Total of N-P-K added in 12-week following recommended dosing:

  • N: 3.82 grams
  • P: 3.70 grams
  • K: 6.44 grams
  • Micronutrients

Key remarks: Follows some “typical” expected profiles of the relative N-P-K ratios, where N is needed more in the vegetative stages, Phosphorus more at late vegetative and early blooming stages and K more at late blooming and ripening stages.

What I like: It comes in 3 parts and thus offers flexibility in adjusting dosing. I like that Nitrogen falls from early blooming stage while K is higher than N. That is important especially at ripening where K would help in having better quality fruit.

I also like that Phosphorus increases from late vegetation and then drops from mid bloom; that peak period is when the plant mostly absorbs P so after that there is not much need for it.

What I do not like: Although K is higher than N, it is a bit too high in the vegetation and early blooming stages which may be wasted unless you adjust the K added in the nutrient solution.

Key reported issues by users: Some issues with shipping: broken bottles from some retailers or bottle volume between description and phots not always match. So be aware.

Element Nutrients

Element Nutrients is my second-runner of fertilizers. They do not come in multi-parts; you buy them separately and it works just fine. It is in dry powder form and it comes in containers from as little as 200grams (7oz) to as big as 20kilos (44lbs), so pick the one that suits you.

I have analyzed how much of the key nutrients is added across a typical 12-week feeding schedule if the recommended by the manufacturer dosing is followed.

Total of N-P-K added in 12-week following recommended dosing:

  • N: 6.86 grams
  • P: 7.08 grams
  • K: 14.37 grams
  • Micronutrients and Humic acids

Key remarks: Provides very high N, P and K compared with other products from mid flowering stage, which is too high.

What I like: It can work even with just the base product (Complete Crop) which has most of the micronutrients too. I also like that the trio comes with a specific product (Myco+) for root health (very important). It also has humic acids (not many fertilizer have) which enhance the uptake of nutrients and thus plant growth. 

What I do not like: It provides excessive levels of all elements if the recommended dosing is followed and some of it may be wasted and there is danger of nutrient burn.

In addition, during ripening, N is still added in which will not help producing firm and quality fruit. I suggest you adjust the dosing yourself to reduce N at ripening stage and perhaps try half the recommended dose of the Flower Power as it is too strong.

Key reported issues by users: Too strong, dosing should be reduced to avoid nutrient burn (of course depending on the plant) supporting my analysis finding of excessive nutrient content following the recommended dosing.

General Hydroponics Maxi Series

Maxi Series from General Hydroponics is a 2-part dry fertilizer. It comes in 2.2 lbs, 16 lbs and 50 lbs. This product is essentially trying to provide what the Flora Series from General Hydroponic does, but with easier application as it is only 2 parts that you need to mix. But there are some notable differences and points you should be aware.

I have analyzed how much of the key nutrients is added across a typical 12-week feeding schedule if the recommended by the manufacturer dosing is followed.

Total of N-P-K added in 12-week following recommended dosing:

  • N: 3.26 grams
  • P: 4.08 grams
  • K: 5.94 grams
  • Micronutrients

Key remarks: P is significantly increased towards the late flowering and ripening stages which is too high. Otherwise, N is progressively reduced and K is always higher than N fitting expected generic and “typical” ratios.

What I like: It is simple to apply as it is comes in only two parts. I like that Potassium (K) is higher than Nitrogen (N), that N reduces at the late bloom and ripening stages to avoid antagonistic problems with K.  

What I do not like: It seems that Phosphorus (P) is added in excess at the mid blooming stage while it would mostly be needed at the end of vegetation and early blooming stages when the plant takes up almost all its P needs. The excessive Phosphorus at later stages would most likely be wasted.

Key reported issues by users: Perhaps more Calcium is needed if your plants are heavy fruiting. It does not dissolve easily so grinding it helps. It leaves residue because it is dry rather than liquid, so not suitable for hydroponics which use nozzles like aeroponics.

Fox Farm Grow Big, Big Bloom, Tiger Bloom

Fox Farm offers a 3-pack of the Grow Big, Big Bloom and Tiger Bloom in liquid form and in different container sizes; pint, quarter and gallon.

I have analyzed how much of the key nutrients is added across a typical 12-week feeding schedule if the recommended by the manufacturer dosing is followed.

Total of N-P-K added in 12-week following recommended dosing:

  • N: 4.50 grams
  • P: 7.00 grams
  • K: 10.40 grams
  • Micronutrients

Key remarks: Maintains stable N-P-K from week 6/7 onwards while they should be adjusted for fruit ripening. It has twice as high K compared with N which is too much. Generally K is too high for the first 6 weeks and P too high for weeks 7-12.

What I like: It comes in 3 parts and thus offers flexibility in adjusting dosing. Also, Big Bloom is an “Organic Input Material” product. While Big Bloom seems to have low concentration of P and K, this is what is readily available. A lot of it is released more slowly as it comes from earthworm castings and bat guano. Also, good that Potassium is higher than Nitrogen and that Phosphorus jumps at early blooming, BUT… (keep reading).

What I do not like: Potassium (K) is too high and especially in the first weeks most of it will not be useful to the plants. It may be worth adjusting (reducing) the dosing to make it at least equal to N for the first 4 or 5 weeks.

Perhaps Phosphorus (P) could be reduced from mid blooming as in later stages the plant will not absorb a lot more. Generally P seems to be a bit too high compared with the other products except Element Nutrients.

Key reported issues by users: Big Bloom runs out fast – perhaps larger bottles would help or order Big Bloom separately to have more of it. Nutrient burn has been reported which supports my analysis on K and P being too high compared with N at different growth stages.

Humboldt Secret Supplies

(Base A ad Base B should go together, sold as a pack of two)

Humboldt Secret Supplies offer a 2-pack of liquid Base A and Base B which in theory is enough to cover your plants’ basic nutritional needs. However, Golden Tree is somewhat necessary to ensure better results and a more balanced mix. The product comes and in different container sizes; pint, quarter, gallon, 2.5 gallon, 5 gallon.

I have analyzed how much of the key nutrients is added across a typical 12-week feeding schedule if the recommended by the manufacturer dosing is followed.

Total of N-P-K added in 12-week following recommended dosing:

  • N: 5.55 grams
  • P: 4.42 grams
  • K: 4.01 grams
  • Micronutrients

Key remarks: It does seem to be in contrast with all the other products. The level of N is higher than K throughout while in all other products K is higher than N.

What I like: It comes in 2+1 parts and thus offers flexibility in adjusting dosing. The Potassium, important at ripening, is added as a separate product that does not contain N which would otherwise work antagonistically. For fruiting plants, perhaps increasing the Potassium dosing to about 50% higher than N from week 6 onwards would benefit the quality of the fruit.

What I do not like: The recommended dosing provides a significant level of Nitrogen, a lot higher than Potassium throughout. High N will lead to over-growth problems and some antagonism with Potassium, proven to be problematic at the ripening stage. Nitrogen should be higher at the vegetative stages (up to around week 6) while after that K should start increasing above N to about 50% higher.

Key reported issues by users: Base A and Base B make the mix too acidic. Requires considerable amounts of pH Up to correct it.

The basics of hydroponic nutrients

N-P-K ratio: it denotes the percentage by volume of the 3 key nutrients (Nitrogen, Phosphorus and Potassium). It is the first you see on most nutrient products (fertilizers) in the form of 3 numbers separated by 2 dashes (e.g. 24-8-16) – if it is not on the front label, then look at the analysis at the back label. So a fertilizer 24-8-16 means that by volume it contains:

  • 24% Nitrogen (N)
  • 8% Phosphorus (P)
  • 16% Potassium (K)

So the total would be 48% by volume. The remaining 52% is other nutrients such as Boron, Copper, Iron, Magnesium etc as well as some inert substances used to make the nutrients soluble and chemically stable.

Calcium Nitrate – Ca(NO3)2Plants grown in soil get calcium from the soil; but in hydroponics, you need to add this in the form of Calcium Nitrate. It helps plants building strong cell walls. That means plant stems are stronger and will not snap or bend because of weight. But because Calcium Nitrate is a source of Nitrogen too, be careful with the total Nitrogen as most likely you will add it with other fertilizer as well. Some good products for Calcium Nitrate are the Greenway Biotech in solid form and the EZ-gro in liquid.

Magnesium Sulphate (you will also see it as “Epsom salt”): it is used to correct magnesium deficiency. Magnesium is essential in the photosynthesis process and the development of sugars in plants; leaves get greener and fruits get tastier. If you use a fertilizer designed for soil, it could lack magnesium. In that case you need to add it in the form of magnesium sulphate. If you use a nutrient product specifically designed for hydroponics, most likely it will have magnesium sulphate. Bear in mind, that magnesium sulphate is pH neutral; it does not make an impact on the solution’s pH. A classic choice is the Epsom Salt from Power Grow .

Macro and Micro nutrients

All are necessary for hydroponics, as there is no soil to provide them at all. Macro-nutrients are those that are required in larger quantities and micro-nutrients in much smaller quantities, thus also called “trace elements”. Missing one nutrient is going to cause problems to your plants. All fertilizers made for either hydroponics or soil will have N-P-K. Those specially made for hydroponics will have all nutrients in either 1 product or in 3 products that you need to mix. Products made for soil may or may not have the micro-nutrients, and likely not have Magnesium, Calcium and Sulphur.

How much to feed the plants

Depends on the growth stage. Each nutrient product will have instructions of how much to add in your nutrient solution depending on the growth stage. But generally speaking, for most typical hydroponic plants you should know that:

  • Germination needs a light mix of nutrients- small plants need small amounts of nutrients
  • As plant growth progresses, the nutrition needs increase
  • Nitrogen is mostly needed at the Vegetative/Growth stage until Early Bloom when the plant and roots increase in size. Nitrogen needs reduce after that.
  • Phosphorus is mostly needed during the Early Bloom and Flowering stages but in much smaller quantities compared with Nitrogen. More Phosphorus will not lead to bigger better flowers, just in more small ones which will not lead to better yields.
  • Potassium (K) is generally required in higher quantities compared with Nitrogen, especially in the Fruiting stage (fruit formation and fruit growth) – roughly 50% more. But adding excessive Potassium can hinder the absorption of Calcium and Magnesium.
  • However, the higher Potassium quantity compared with Nitrogen in the Fruiting stage, does not necessarily mean that the overall total Potassium quantity to be added in the nutrient solution over the course of 12 weeks will also be more than Nitrogen.

For the 5 shortlisted fertilizers, the graphs below present the N-P-K quantities added in a nutrient solution for a period of 12 weeks. The graphs serve illustrative purposes and are the result of analysis I performed accounting for each product’s N-P-K ratio and the manufacturers recommended dossing. As it is clearly seen, each product is different. The amount of each main element (N, P, K) that is added in the nutrient solution differs significantly between the different products both in the profile across 12 weeks and cumulatively. As the research community has not definitively concluded what is the right N-P-K ratio per growth stage, it is hard to judge only from it. There are though some facts around how much to feed the plants as described above that describe generic and “typical” expected N-P-K ratios.

What to consider when choosing hydroponic nutrients

Liquid or dry

Liquid nutrients are essentially ready made products made from solid nutrients (usually in powder form) mixed in water. They can be added directly into the water in the reservoir in the right ratios. The solid nutrients require you to mix them in the right quantities to create concentrated liquid fertilizer to then add into water. So with liquid fertilizer you skip the initial step of mixing different solid nutrients which can be tricky if you have less experience. However, for commercial scale hydroponics it is better to opt for solid nutrients as they are cheaper per weight.

1-part or 3-part products

If you are just starting hydroponics, 1-part nutrient products are convenient. You only need to add the right amount of 1 product in water, stir and feed it to your plants. They can be either in liquid or dry form. But they come at higher price per volume or weight and they are not perfectly balanced for the different needs of each growth stage. They cab ne good for simple hydroponic plantation, e.g. leafy greens but not so much for fruit bearing plants.

3-part products offer 3 separate packages (e.g. bottles if in liquid form or sacks if dry); each package focuses in one of the main 3 elements (N, P, K) but will have the other elements in smaller quantities. You will need to mix a specified volume or weight (depending on whether the product is in liquid or dry form) from each of the 3 parts and then if the pH is high correct it by adding tiny bits of “pH Down”.

The benefit of the 3 part products (there are 6-part, 10-part as well) is that you can adjust the dosage based on instructions (feed charts) from the manufacturer to accommodate the specific needs of the growth stage: germination, early grow, late grow, early fruit formation, fruit growth, fruit ripening.

Natural or synthetic

Natural hydroponic fertilizers denote that the nutrients have been derived from natural sources, such as extracts (e.g. molasses) and manure or compost. There are commercially available products which offer more certainty around dosing but some products may be more difficult to dilute in water which will leave excessive sediments in the system.

On the other hand, the synthetic nutrients are all derived from the petrochemical industry thus not so eco-friendly. But they offer consistency and very good solubility.

I would suggest that you start with the synthetic ones to get experience in handling nutrients for hydroponics and then start experimenting with natural products or even make your own from sources like compost, blood meal, fish bone etc.

All-purpose or hydroponic-specific products

An all-purpose fertilizer will most likely lack some of the elements that the plant can get from the soil or have those nutrients in smaller quantities compared with hydroponic-specific fertilizers. So if you use an all-purpose fertilizer in hydroponics, you need to add those missing (or in deficit) nutrients. For example, you may need to add Calcium and Magnesium using separate products like CALiMAGic from General Hydroponics or Cal-Mag from Bloom City.

FAQs

  • Can hydroponics work without nutrients?
    • No, definitely not. Plants need nutrients to survive and grow. Just water will not be sufficient. There are though some hydroponic products which offer growing media enriched with nutrients , such as the Click and Grow.
  • Can I use nutrients made for soil?
    • Yes you can, but they need to contain at least the micro-nutrients (Boron, Copper, Iron, Manganese, Molybdenum, Zinc). And then you need to top it up with Calci8uum Nitrate and Magnesium Sulphate to compensate for the lack of the remaining macro-nutrients (Calcium, Magnesium and Sulphur). If you are keen to read more on nutrient deficiency and nutrients, check out my post on the 12 Plant Nutrient Deficiency Symptoms and How to Fix Them.
  • Are hydroponic nutrients safe?
    • Ensure you buy nutrients from reputable brands with appropriate and adequate information on safety and application instructions, even better if they have source details and manufacturing process information.
  • Are there natural hydroponic nutrients?
    • Yes there are. The natural nutrients denote the origin of the nutrient element being from a natural source such as extracts (eg molasses) and manure or compost. There are commercially available products which offer more certainty around dosing but you may also make your own, but that is a lot harder with uncertain results and not guarantee for maximum yield.
  • Are there organic hydroponic nutrients?
    • No to be precise. There are organically derived nutrients that make up the commercially available products but the certification of the final product as organic is not there yet. But you should try the products that have certifications for the input substances if you are prepared to pay more.
  • Do I need to change the nutrient solution and reset it?
    • Yes you need to, but not very often. In other posts, I recommend changing the nutrient solution every 3-4 months. For indoor hydroponic systems that would, on average, coincide with the end of the growth cycle of most of your plants, or with excessive nutrient sediment and algae growth in the system. In those cases you need to empty the nutrient solution and clean the system before resetting. You will find that some people suggest to almost never change the nutrient solution as you would get rid of the good bacteria which keep algae and fungi under control. It may be true in a certain extent, but then from a practical perspective unless you are very experienced in mixing nutrients to a nutrient solution which has depleted but still some quantity of a numbers of elements, then it is safer to restart with new fresh batch.
  • Liquid or solid hydroponic nutrients? Which one is best?
    • There is no best or worse in this case. There are only pros/cons that fit in your particular situation.
    • The liquid nutrients are essentially solid nutrients diluted in the right concentration. If you choose to have the solid ones, you need to mix them accurately (N,P,K and trace elements) in the right proportions and then dilute them in the right concentrations. That requires experience and a digital scale! Because it is harder to get perfect accuracy in mixing them, it is more likely to have nutrient sediments/residues compared with the liquid ones. But they are cheaper per weight, cheaper to transport and store.
    • The liquid nutrients on the other hand are ready to use, though you need to apply the right concentration in the solution. I would recommended this option especially if your hydroponic system is an indoor medium scale only for your family’s needs or you are just starting. If you are planning to go big-scale, then I think dry nutrients are the way to go due to cost.
  • What is the right pH and TDS/PPM/EC of the nutrient solution?
  • Do I need to test the pH and how do I adjust pH of the nutrient solution?
    • The digital pH meters are quite handy. You place the probe in the nutrient solution and an indication comes up on the display. Use the “pH Down” or the “pH Up” if you need to decrease or increase the pH level. All hydroponics systems and nutrients come with relevant instructions about correction pH levels. If you find that each time you try the correction with the “pH Down” or the “pH Up” is only short-lived, then there is a more fundamental reason throwing pH out of balance. Recommended action is to flush the nutrient solution and make a new one as too much experimentation with a working nutrient solution may shock your plants.

About me...

I am a qualified Agricultural Engineer and Mechanical Engineer with years of industry experience. I approach problems from a practical perspective backed up with hard data. I understand that there is no one-size-fits-all in most things, hence I allow for variations in my analysis to get tailored solutions to you.

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My top nutrient pick

My top pick is the General Hydroponics Flora Series primarily because it would require little adjustment in dosing in order to deliver the “expected” typical and generic levels of N-P-K ratio (see earlier section on “How much to feed the plants”).

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