The Ultimate Guide to Hydroponic Nutrient Solution

You’ve chosen your hydroponics system. You agonised over the perfect growing medium. Now it’s the final decision. The most sciencey part: choosing and using your nutrient solution.

Don’t worry. Nutrient solutions initially seem mind-boggling with so much chemistry and acronyms and numbers being thrown around, but once you learn a few principles, you’ll be feeding your hydroponic plants like a pro.

In this article, you’ll find out:

  1. Hat hydroponic nutrients are,
  2. How macro and micronutrients contribute to a healthy plant,
  3. What to consider when choosing your nutrient solution,
  4. Other factors that you will need to know when mixing the nutrient solution,
  5. And finally, the easiest step, actually mixing hydroponic solution to feed your hydroponic plants.

Let take a look at this video:

What Are Hydroponic Nutrients?

Plants, like humans, need certain amounts of nutrients to live and grow. When you grow plants in soil or potting mix, the soil provides a lot of those nutrients. But when you grow with hydroponics, you are solely responsible for providing all the nutrients that your plants need.

Which seems pretty intimidating, I know.

This is where hydroponic nutrient solution comes in. It’s a water-soluble solution that you mix with water to feed your plants. In other words, a hydroponics fertiliser.

You can buy it pre-formulated in bottles or as dry mix from manufacturers, or, if you’re planning a large hydroponics garden or commercial venture, you can make your own.

So what are these vital nutrients?

Macronutrients

The Ultimate Guide to Hydroponic Nutrient Solution

Macronutrients are the nutrients that plants need in large quantities. For plants, these are Nitrogen (N), Phosphorous (P), and Potassium (K), otherwise referred to as NPK.

If you look on fertiliser and nutrient solution bottles, you’ll see something like this: 2-1-6 or 0:5:4. That lists the NPK ratios, or basically how many parts are nitrogen, phosphorus, and potassium. In the first example, 2-1-6, that means 2 parts nitrogen, 1 part phosphorous, and 6 parts potassium.

The specific ratios depend on your plant’s stage of growth, but we’ll get into that further down.

Nitrogen is responsible for the formation of leaves and stems. Nitrogen is especially important for growth. A lack of nitrogen results in yellow leaves, but too much nitrogen can burn your plants’ roots.

Phosphorous builds healthy roots, transports energy through the plant, and ensures proper flower and seed formation.

Potassium activates the stomata for breathing in CO2, produces ATP, and regulates chlorophyll. Potassium is responsible for a lot of the photosynthesis process.

Micronutrients

The Ultimate Guide to Hydroponic Nutrient Solution

Micronutrients are the nutrients that plants need in small quantities but are equally important as the macronutrients. Most fertilisers for soil-based growing focus on the macronutrients and don’t include micronutrients, since it’s assumed these will come from the soil and other amendments, which is why you can’t just use fertiliser.

Boron and calcium form cell walls. Boron also assists in sugar transport and the production of amino acids.

Copper activates the enzymes required for respiration and photosynthesis.

Iron is essential for chlorophyll formation and enzyme composition, and assists in energy production.

Manganese influences chloropast production and helps with photosynthesis.

Magnesium catalyses the growth process, helps the plant absorb sunlight during photosynthesis, and acts as a phosphorous carrier.

Sulfur synthesizes protein, acts as an organic fungicide, and helps fruiting, seeding, and water uptake.

Zinc also helps to form chlorophyll and some carbohydrates, is essential in the formation of auxins, assists respiration and nitrogen metabolism.

These are just some of the functions of each nutrient.

You don’t need to memorise all of this, but knowing what each nutrient does will help you identify deficiencies and when you use too much.

What to Consider When Choosing Nutrient Solutions

The Ultimate Guide to Hydroponic Nutrient Solution

Formulas for Vegetative and Flowering Stages

Remember above when I said not to worry about NPK ratios yet? That’s because the ratio of macronutrients depends on what stage your plant is in.

You can get really complex, dividing your plant’s life into many sub-stages. But basically, your plant has two stages: vegetative and flowering growth.

Vegetative growth is when your plant is focused on growing green leaves and stems. In this stage, your plant needs lots of nitrogen to form all those leaves and grow stems. Thus, you give a plant more nitrogen to speed up plant growth.

The flowering stage comes after the vegetative stage, when your plant focuses on reproducing, or, in other words, producing flowers which produce fruit. In this stage, you’ll want to feed your plants higher amounts of phosphorus to help develop all those flowers and fruits.

Do all vegetables go through both stages?

A lot of the vegetables you’ll grow will only go through the vegetative stage before you harvest. These vegetables include anything that you eat the leaves or roots of, like lettuce, spinach, most herbs, kale, carrots, turnips, and beets.

But some vegetables (which are actually fruits) must then go onto the flowering stage to produce what we eat. So, if you’re eating fruit filled with seeds, you’ll need the flowering stage. These include tomatoes, strawberries, cucumbers, zucchini, squash, and melons.

When growing vegetables through the flowering stage, you’ll need to use two different formulas.

If you are buying from a manufacturer, then this is all taken care of. You’ll buy a set of bottles or bags which will have in the name Grow or Vegetative and Bloom or Flower. Use whichever for what stage your plants are in.

This also means that you should avoid having plants of different vegetative stages using the same reservoir. So don’t grow your tomatoes in the same setup as your lettuce. It’s easier, in the long run, to set up two systems.

Liquid or Powdered Nutrient Solution

The Ultimate Guide to Hydroponic Nutrient Solution

Manufactured nutrients come in two forms: liquid and powdered, also referred to as wet and dry.

Liquid solutions are the easiest to work with because they:

  • Easily mix and dissolve in water
  • Often come with pH buffers, so the nutrients will balance your pH level for you
  • Easier to mix the right concentration without additional equipment
  • More expensive than powdered
  • Cost more to ship and are heavier
  • Are great for beginners and home growers!

Powered solutions are a powder that you dissolve in water. They’re trickier to work with because they:

  • Won’t always dissolve properly, so they may clog your system
  • Won’t balance your pH for you
  • Requires a precise scale
  • Less expensive overall than liquids
  • Store for longer
  • Cheaper to ship
  • Better for large-scale home growers and commercial growers

Why Do Liquid Nutrients Come In Separate Bottles?

Liquid nutrients often come in separate bottles (usually two bottles of macronutrients and one bottle of micronutrients) because certain micronutrients can react when combined with certain macronutrients in concentrated form, as liquid nutrient solutions are. Once you dilute them in water when preparing your nutrient solution, these compounds are more stable.

(Powdered compounds don’t have this problem as they are more stable, thus why they store for longer.)

While you can get nutrient solutions in one bottle, these are generally more expensive and you can’t tweak them for each growth stage.

That being said, one-part bottles can be very handy when you’re just starting off growing as they’re simpler to use.

Can You DIY Hydroponic Nutrients?

You can create your own DIY nutrient solution, but I recommend this only if you:

  • maintain a large hydroponics garden,
  • want to use organic nutrients,
  • have been growing hydroponics for a while and/or plan to continue years into the future, or
  • are a commercial grower.

Making your own DIY solution will be more expensive upfront, as you have to spend hundreds of dollars on the raw ingredients. But since you’re using a large amount of nutrient solution over the long-term, you’ll end up saving up to 90% off the same quantity from a manufacturer.

If you’re just starting out or have a small system, then buying a premade solution will save you a lot of time and effort, especially in the beginning when you have a thousand other things to worry about. (You can always try DIYing once you get the hang of it and you’re sure you’re in for the long haul.)

Science in Hydroponics has a free calculator for figuring out how much nutrients you need, how to obtain each of the nutrients, and a hydroponic nutrient solution recipe.

You can also make your own DIY organic nutrient solution, as you’ll see down below.

Can You Use Miracle-Gro Instead?

The Ultimate Guide to Hydroponic Nutrient Solution

This is a hard maybe.

Using Miracle-Gro has several challenges as it’s:

  • Harder to dissolve and can block tubes.
  • Only contains NPK. You can mix it with Epsom salts to provide more nutrients, but you’ll then need to watch for nutrient deficiencies and add those nutrients in as problems arise.
  • Only formulated with one NPK ratio, so you can’t adjust for different growth stages.

There is, however, one hydroponics system where you can use Miracle-Gro: the small-scale Kratky method. There are no tubes to block and you’re only growing lettuce and leafy greens for a short time so nutrient deficiencies have less time to crop up.

Can You Use Organic Hydroponic Nutrients?

Most of the nutrient solutions most popular in hydroponics are made from synthetic chemicals. But you can grow hydroponics with organic nutrients but it’s not a straight swap.

Just like with Miracle GRO, you can’t just swap them in. Organic fertilisers are meant to be used in soil with the aid of beneficial microbes. These microbes break down the organic components into nutrients that the plants can then absorb. If youtry to just dissolve organic fertilisers, you’re going to block all your tubes and your plants won’t be able to absorb the nutrients anyway.

Organic nutrients needs to have a system with:

  • An air pump to oxygenate the water and avoid anaerobic conditions, which decomposes your plants’ roots and stinks
  • A habitat for for beneficial bacteria to live, whether in a bio-filter or growing mediums like coconut coir and clay pellets

You can make organic hydroponic nutrients available in three ways:

  • Using aquaponics where you feed the fish organic food, and they and the ammonia they produce will convert into nutrients.
  • Making vermicompost tea (or other high quality organic compost) where the worms render the organic matter into useable nutrients, and the tea makes it water-soluble. The downside is that you don’t know the nutrient content in exact ratios (so your mixture may be too weak to sustain plants) and you may need to add mineral salts and nitrogen to increase necessary nutrients.
  • Using a recipe of fish emulsion, liquid seaweed, and bloodmeal using liquid concentrates or water-soluble components.

What Are The Best Liquid Nutrient Solutions For Beginners?

The Ultimate Guide to Hydroponic Nutrient Solution
  • Dyna-Grow GROW is an all-in-one bottle hydroponic solution for all your greens.
  • General Hydroponics (FloraGro, FloraBloom, FloraMicro) is one of the most recommended brands for beginners. You get more control over the stages with a quality brand that is still easy to use.

Other Factors You Need to Control

Nutrients and nutrient solution are only part of the story. There are a few other things you need to do when preparing your nutrient solution.

Temperature of Water

Plants grow best when the water and nutrient solution is at room temperature. Too cold, and the roots will go into shock and die. Too hot, and you’re cooking your plants.

This is pretty easy in a climate-controlled grow space, but if you’re growing outside or without AC or heat, then you’ll need to heat or cool the nutrient solution periodically. Or you may need to equip it with heaters or shade.

pH Level

The Ultimate Guide to Hydroponic Nutrient Solution

pH level is basically how acidic a solution is on a scale of 0 to 14, with 7 as neutral. So anything less than 7 is on the acidic side while anything above 7 is alkaline or base.

While the best pH level depends on what you’re growing, in general, you want a level between 5.5 and 6.5. (Most plants prefer slightly acidic levels.)

Why Is Ph Level Important?

pH level is important because nutrients can only be absorbed by a plant at certain pH levels. Each nutrient has a different but overlapping ideal pH range for absorption. By getting the pH level into your plant’s sweet spot, your plants will be able to absorb the nutrients in the most efficient way.

Outside of that range, your plants will become sickly as they can’t absorb key nutrients. Also, if your acidity is too high (below 5.5), the acidity level can burn your plant’s roots.

How close you need to get to an ideal number depends on your scale. If you’re growing commercially where time growing is money, getting as close to ideal means faster plant growth.

If you’re growing at home for fun, then save yourself time and anxiety by getting with the range.

How To Test Your Ph Level

The Ultimate Guide to Hydroponic Nutrient Solution

To test the pH level, you have three options:

  1. pH Testing Strips. The most inexpensive option, pH testing strips are a paper with a series of indicator bars that when exposed to a liquid, change colours. The colour bars indicate the pH level. Strips are the least precise way to test pH.
  2. pH-Sensitive Solution. Instead of a strip, you add drops of your nutrient solution mix into this solution. The solution turns colour based on the acidity and you compare that colour to the included colour metre to determine the pH level. This option is the middle ground for both price and precision.
  3. pH Testing Metre. The most expensive option, but also the most precise. You’ll need to calibrate it often, but once you get used to that, the process is pretty quick. Once calibrated, you simply place the electrode into your solution and it will give you a precise number on its screen.

Once you know the initial pH level of your nutrient solution mix (including the water), you can then use pH Up and Down (avoid contact with your skin!) to adjust the pH level to your target range.

Some premade liquid nutrient solutions come with pH buffers, which adjusts your pH level for you. Just another reason why they’re the beginner-friendly option.

Electrical Conductivity (EC)

The Ultimate Guide to Hydroponic Nutrient Solution

Electrical conductivity measures the concentration of the nutrient solution in your mix which is then converted into parts per million (PPM).

PPM helps you figure out if your nutrient solution is at the right concentration, both when you’re initially preparing the nutrient solution and in monitoring when it’s time to prepare a new batch of nutrient solution.

To measure EC, you’ll need an electrical conductivity meter. EC meters come at a variety of price points, so you’ll be able to find the right one for your budget.

Sounds great, right? There is one major downside.

The Problem of Hard Water

EC only measures how much stuff is in the water, not specific nutrients, or even just your nutrient solution as a whole.

If you have a lot of minerals in your water (like with hard water), then the EC metre will measure that as part of the PPM. So you could have a really weak mixture but the EC reads as fine.

Before you add the nutrient solution, test the EC of your water to see how hard your water is. Ideally, you want to start with the PPM as close to 0 as possible.

If the PPM is low, you can adjust your calculations for the nutrient solution.

But if it’s higher, then you will want to use filtered or distilled water. You’ve probably noticed how your water leaves a white scum on your shower head or in your kettle from mineral build-up. You don’t want that happening inside your tiny tubes and in your grow bed.

PPM Doesn’t Measure Specific Nutrients

The other thing you need to keep in mind is that because the EC doesn’t measure specific nutrients, you only know the concentration as a whole, not by particular nutrients. So if you’re testing to see if it’s time to replace the nutrient solution in your system, you won’t know how much remains of each nutrient and whether it’s still in the correct proportions.

The best thing to do in this case is to err on the side of caution. And make sure you’re using the right ratios at the right stage.

How to Prepare Nutrient Solution

The Ultimate Guide to Hydroponic Nutrient Solution

Now we know what’s in nutrient solutions, how to choose the best nutrient solution for your circumstances, and the other factors that go into preparing your nutrient solution. Now it’s time to do it!

The above is a lot of things you need to know, but the actual process is pretty simple. Once you’ve been growing for a while, it’ll all become second nature.

Tools Needed to Prepare Nutrient Solution

  • A bucket or container for mixing the nutrient solution
  • Something to stir with
  • Water (tap, filtered, or distilled)
  • Nutrient Solution
  • If your nutrient solution doesn’t come with a pH buffer:
    • pH measuring device (strips, solution, metre)
    • pH Up and pH Down
    • Gloves and safety glasses
  • EC metre
  • A precise scale (if using powdered nutrient solution)

How to Mix Nutrient Solution

  1. If using tap water, leave the tap water in the container for 24 hours to allow the chlorine to evaporate.
  2. Check the PPM of your water.
  3. Follow the instructions of your nutrient solution’s manufacturer.
  4. Check the EC concentration of nutrients until you hit the sweet spot.
  5. If your nutrient solution doesn’t come with a pH buffer: check the pH level, then while wearing gloves and protective glasses to protect yourself from burns, use pH Up or Down. Then check your pH level. Repeat until you hit your target range.
  6. Add the nutrient solution mix to your hydroponic system.
  7. Check regularly.

Conclusion

After reading through carefully (you did read through the whole thing, right? Not just skimmed?), you’ll know why nutrient solution is so important and all the steps you need to properly mix nutrient solution. There’s a lot of science terminology, but underneath it’s pretty simple.

So now go grow the hydroponics garden of your dreams.

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Jill Sandy

Jill Sandy

Jill is a sustainable focus gardener. She loves decorating her home backyard with beautiful landscape design and creative garden care techniques she develops herself. You can reach her at [email protected]

Chanh Ho (MD, MPH)

Chanh Ho (MD, MPH)

Chanh is our Head of Medical Review. He is a research physician at Oxford University Clinical Research Unit. After accomplishing the program of level 1 sub-specialty in Pediatrics, he was awarded the Chevening Scholarship for his Master’s degree of Public Health in the University of Edinburgh in 2019

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