Hydroponic Nutrients and Fertilizers 101 (Which Is Best?)

Hydroponic Nutrient Basics

Plants need nutrients to survive and thrive. 

In hydroponics, we need to put the perfect balance of nutrients into our systems or our plants just won’t make it. We don’t get any help from the soil which naturally has some of these nutrients, it’s all up to our fertilizer.

Before I break down everything you need to know about hydroponic nutrients, I want to show you which nutrients plants need specifically, with a bit of info as to why your plants need them in the first place.

Macronutrients

Nitrogen (N)

An essential part of all amino acids in plant structures. Needed for fast growth and development. 

Phosphorus (P)

Essential for plant growth, fruiting, photosynthesis, and nutrient movement in the plant, among many other things. 

Potassium (K)

Maintains pressure inside plant cells which prevents wilting. Helps plants release waste gasses and water vapor. Very important for fruiting plants.

Calcium (Ca)

Holds cell walls together and helps in their formation with new growth. 

Magnesium (Mg)

Required by many enzymes. It is the central atom in the chlorophyll molecule which carries out photosynthesis and gives plants their green color.

Sulfur (S)

An integral part of all plant proteins and some hormones. It is used in the formation of some oils and volatile compounds in alliums like garlic and onions.

Micronutrients

Boron (B)

Needed to synthesize cell walls and for cell division. Also, important for seed, fruit, and pollen development, among many other things.

Zinc (Zn)

Important for many plant functions, including converting starches into sugars, growth regulation, and stem elongation. Also helps with cold-resistance.

Manganese (Mn)

Used in respiration, photosynthesis, and nitrogen assimilation. Also involved in root cell elongation and protects against root pathogens.

Iron (Fe)

A part of some plant enzymes and pigments. Helps with nitrate and sulfate reduction and energy production.

Copper (Cu)

Intensifies flavor and color in vegetables and flowers. Essential for several enzymes, respiration, photosynthesis, and more. 

Molybdenum Mo)

Needed by enzymes that synthesize amino acids. Also helps to make inorganic phosphorus usable by the plant.

Chlorine (Cl)

Chloride, the anion of chlorine, is needed for plant metabolism, osmosis, photosynthesis, and ionic balance within plant cells.

Primary, Secondary, and Micronutrients

There are different classifications of nutrients based on their importance in plant growth.

The primary nutrients are nitrogen (N), phosphorus (P), and potassium.

Secondary nutrients are essential for growth, but in smaller quantities than the primary nutrients. These are calcium (Ca), magnesium (Mg), and sulfur (S).

Lastly, plants need a variety of micronutrients. As the name suggests, only a tiny amount of these nutrients are needed, making them less important than primary and secondary nutrients. The micronutrients plants need are boron (B), zinc (Zn), manganese (Mn), iron (Fe), copper (Cu), molybdenum (Mo), and chlorine (Cl).

A What is NPK?

NPK stands for nitrogen (N), phosphorus (P), and potassium (K). These are the primary three nutrients needed by all plants to grow and survive.

Because of its importance in hydroponic growing, you will see NPK referenced frequently. Understanding NPK is the first step in understanding plant nutrition.

Hydroponic fertilizers will usually have three numbers printed on the front of the bag or bottle, something like 4-18-38. This number represents the balance of NPK. This means 4% of the fertilizer is nitrogen, 18% is phosphorus, and 38% is potassium. 

Different Nutrient Needs of Leafy and Fruiting Plants

In general, nitrogen is the driving nutrient in foliage growth and therefore is especially important for leafy greens like lettuce, spinach, bok choy, and kale, as well as herbs and microgreens.

Leafy plants also do well with higher levels of potassium which helps with many essential functions including growth and structure.

A good balance of nutrients for leafy greens is 24:6:25 like this Lettuce Greens and Herbs fertilizer blend.

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This blend contains a complete nutritional formula with five macronutrients and six micronutrients specially balanced for leafy greens and herbs.

Or, for something more flexible, a ratio of 10-5-14 like in this MaxiGro all-purpose fertilizer for vigorous growth will work great for greens.

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Fruiting plants, like tomatoes, cucumbers, strawberries, peppers, and the like, need a slightly different combination of nutrients. 

Starting with a higher concentration of potassium helps your plants during their fruiting stage. Potassium helps plants move water and sugar inside themselves, improving sweetness and overall quality.

As a plant comes closer to producing fruit, its nitrogen requirements increase. Giving plants adequate nitrogen at this stage will increase the size of fruits.

For a well-balanced fertilizer for fruiting plants, I’d recommend using a 4-18-38 blend. You will need to mix the main fertilizer with calcium nitrate and epsom salt before using it in your hydroponic system.

All three of those essential ingredients can be purchased in a bundle like this one from Mastergrow (more on how to use these below).

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Types of Nutrients

There are different ways to buy your fertilizers, mainly, in liquid form, as a ready-made powder, or separated into different components so you can mix them yourself.

Liquid vs. Powder vs. Homemade

Liquid fertilizers are the easiest to deal with as very little preparation is required. The nutrients in these concentrates are pre-dissolved so vigorous mixing isn’t necessary. 

With liquid, you don’t need to go measuring and mixing several ingredients to get the right mix.

However, the downside of using liquid fertilizer is that it costs more to ship because of its water weight. Also, you sacrifice some ability to customize the fertilizer like you can with homemade ones. Lastly, liquid fertilizers are usually the most expensive.

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Powder fertilizers are pre-mixed bags of dry ingredients. All you need to do is dissolve them in water and you’re ready to go. 

These are still quite convenient as no complicated measuring, mixing, and balancing is required. You just follow the instructions on the bag and mix some of the powder with water.

Because they are completely dry, they are cheaper to ship than liquid fertilizers.

The only downside with powder fertilizers is they are pricey. Special pre-made blends cost a premium, just like with liquid fertilizers.

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Finally, taking the DIY route will require a bit of work, but it can be rewarding. 

Many hydroponic growers swear by homemade fertilizer because it offers flexibility and great value. You won’t get a better price on fertilizer than if you buy bulk ingredients and make it yourself.

It isn’t as complicated as many imagine. You can buy a bundle of everything you will need all in one, follow the instructions, and mix them together without any special equipment.

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Keep reading for a full guide on how to use this Masterblend kit and mix your own fertilizer at home.

The Best Hydroponic Nutrients By Plant Type

The best hydroponic fertilizer for leafy greens and herbs like lettuce, spinach, kale, endive, swiss chard, arugula, basil, dill, mint, and parsley is all about stimulating foliar growth and getting those leaves built up fast. 

For leafy greens and herbs, I recommend using this Lettuce Greens and Herbs Mix. You will need to combine the two parts of this powdered fertilizer, but all you need is a bucket and measuring cup. This bag makes 128 gallons of nutrient solution.

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For fruiting plants, you will need a slightly different mix of nutrients. The structure of fruiting plants is different from that of leafy vegetables—fruit size, color, and flavor all improve with the right balance. 

For tomatoes, I recommend the Greenway Biotech Tomato Mix. Compared to mixing the ingredients yourself, this fertilizer is super convenient. Everything has been specially formulated and pre-mixed specifically for tomatoes, all you need to do is add water. 

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Peppers need a similar ratio of nutrients but do better with more nitrogen and slightly more potassium. For large, full-flavor peppers, you should use the Greenway Biotech Pepper and Herb Fertilizer. This is another simple “just add water” mix that anyone can use.

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For hydroponic fertilizer for strawberries, more nitrogen is needed, and extra boron helps to get the berries growing fast.

An easy choice is Greenway Biotech Strawberry Fertilizer. This blend is crafted for perfect strawberry growth. And just two pounds of the stuff makes 400 gallons when mixed with water.

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Homemade Hydroponic Fertilizer DIY Recipe

For this recipe, I will be using the Masterblend Combo Kit which includes a 4-18-38 general vegetable and tomato blend, 15.5-0-0 calcium nitrate, and epsom salt.

Buying these ingredients unmixed and in bulk will save you a ton of money in the long run.

All you will need is a 3-5 gallon bucket or similar container, measuring cups, and purified water.

Step 1: Pour one gallon of distilled or reverse osmosis water into a clean bucket.

Step 2: Add 600 grams of Masterblend 4-18-38 Tomato & Vegetable Formula. Mix well. 

Step 3: Add 600 grams of Powergrow 15.5-0-0 Calcium Nitrate. Mix well.

Step 4: Add 300 grams of epsom salt. Mix well. 

This recipe makes a hydroponic fertilizer concentrate, so just one gallon of what you make is good for 250 gallons of nutrient solution. All you need to do is dilute it with water.

To make a general-purpose nutrient solution, add one tablespoon of fertilizer concentrate to one gallon of water.

More Questions About Hydroponic Fertilizer

Do you need different fertilizers for different hydroponic methods?

The hydroponic fertilizer you use depends on the plants you’re growing, not the system that you use. 

Plants’ nutrient requirements are the same regardless of whether they are in a Kratky, NFT, or aeroponic system.

That being said, different hydroponic systems are suited for different types of plants. For example, Dutch buckets, also known as bato buckets, are ideal for fruiting plants like tomatoes, cucumbers, squash, and peppers. These plants need different nutrients than herbs and leafy greens, especially during fruiting when extra nitrogen is key.

So you won’t be picking a fertilizer based on the system you use alone, but what grows well in that system, and ultimately what you decide to put in it, will dictate what fertilizer you use.

Can you grow hydroponics without nutrients?

All plants require nutrients, regardless of whether they are grown in soil, hydroponic systems, or out of a crack in the concrete. You can’t grow any plants without nutrients!

If you were to put a seed or seedling into plain old water without a nutrient solution, it simply wouldn’t grow. The plant would lack the building blocks and fuel that it needs to grow, bear fruit, and survive.

Can I use regular fertilizer for hydroponics?

You can use a fertilizer designed for soil in hydroponics, but it may not be worth the trouble.

The first problem is that regular fertilizer is made to be used in the soil which naturally has nutrients in it. Hydroponic fertilizer is designed to deliver 100% of the nutrients the plant needs. This makes the quantities of nutrients in these products quite different.

Secondly, most soil fertilizers are supposed to be used infrequently. Because of this, they slowly release nutrients. For example, many soil fertilizers contain urea and ammonia salts which need to be broken down by microbes in the soil slowly to provide nitrogen.

Hydroponic systems have no such microbes and hydroponic plants need instantly available nutrients.

A misconception that I hear from time to time is that it could be cheaper to use regular fertilizer instead of hydroponic fertilizer. The prices of the two classes of fertilizer are already comparable, and when you factor in the extra work you will put in to make sure your soil fertilizer is perfectly balanced for your hydroponic plants, it isn’t worth it.

If you want to save money, buy raw fertilizer ingredients in bulk and mix them yourself at home.

Can you use tap water in hydroponics?

If you are going to use tap water in a hydroponic system, you must first test it and treat it.

Tap water has been treated to kill harmful microbes that can make people sick. To do this, the processing plants add chlorine, chloramines, and aluminum sulfate, which you definitely don’t want.

Also, water may come out of your tap at a pH that will harm the plants you are growing.

The best course of action is to use distilled or reverse osmosis water in hydroponics. But, if you insist on using tap water, you will have to go through a few steps to prepare it first.

How do you make tap water safe for hydroponics?

The first step is removing the chlorine. If you leave tap water out in the sun for about a day, UV rays from the sun will break down and remove the chlorine. However, in large quantities, this can be very difficult.

Or, if you want to remove chlorine and chloramine together in one blow, you will need to buy a bottle of chlorine remover, like this.

To balance the pH of your water, you can use the same pH up and pH down you already use in your hydroponic system to balance nutrient solutions.

Lastly, if you have hard water in your tap, you will likely need to purchase an expensive water softener. 

For many growers, especially on a small scale, the best course of action is to use distilled or purified water instead of treated tap water.