Mixing Hydroponic Nutrients: 5 Critical Things You Need to Know


There are a number of hydroponic nutrients that plants cannot function without because they are crucial for the plants’ growth and development. One such nutrient is magnesium that plays a critical role in plant chlorophyll development. Chlorophyll itself is the pigment that enables the plant to carry out photosynthesis using light energy.


Another role of chlorophyll is harnessing green wavelengths which are the reason why most plants are green. Essential nutrients required by plants are either categorized as macronutrients or micronutrients. The amount required by a plant is what defines whether a nutrient is a macronutrient or a micronutrient.



Essential Hydroponic Nutrients

Hydroponic Nutrients
Hydroponic Nutrients, Source


Those in the macronutrient category include oxygen, hydrogen, carbon, nitrogen, calcium, potassium, magnesium, phosphorus, and sulfur. Your plants will get oxygen, hydrogen, and carbon from the water and air around them. Nitrogen, phosphorus, and potassium will come from Hydroponic fertilizers. Secondary nutrients like calcium, magnesium, and sulfur will come from Epsom salts. 


The Micronutrients required by plants like zinc, iron, copper, nickel, manganese, chlorine, molybdenum, and boron will usually come from your hydroponic fertilizer.  Micronutrients are difficult to measure and track unless you have expensive auto dosing and/or special measuring equipment. Most smaller commercial systems and hydroponic home gardeners will dump and flush their systems, and rebalance the pH and hydroponic nutrients to close to what they were as micro-nutrient deficiencies pop up. Then add acids and base and nutrients as required to re-balance the nutrient solution to where it needs to be for those plants.



Hydroponic Fertilizers

Hydroponic fertilizer products must provide uniform information to help consumers compare products. All of their labels carry three numbers that represent the fertilizer’s N-P-K ratio. The ratio proportions are in the following order: nitrogen (N), phosphorus (P), and potassium (K). The N-P-K numbers on the hydroponic nutrients bag reflect each nutrient’s percentage by weight. For example 5-10-10 would represent 5% nitrogen (N), 10% phosphorus (P) and 10% potassium (K). Plants need these more than any other macronutrient.


Nitrogen (N)

Makes leafy growth and rich green color

Calcium Nitrate
Calcium Nitrate, Source



Phosphorus (P)

To develop strong roots and aid in flowering, fruits, and seeds production. Helps plants use other nutrients. Runoff can be the most damaging to the environment and waterways.

Phosphorous, Source



Potassium (K)

Enhances overall growth. Regulates root and top growth.

Potassium Chloride, Source



Examples of different formulas are as follows.

  • 30-00-04    Lawn Fertilizer
  • 05-10-10    Tomato & Vegetables
  • 08-15-36    Lettuce
  • 10-10-10    Flowering bulbs



Epson Salt (magnesium sulfate)

Magnesium is required for plants to grow. Epsom salt is one of the least expensive ways to add magnesium to your hydroponic solution. Magnesium key benefits:

  • Magnesium increases the plant’s ability to absorb other nutrients
  • Makes plants more green and aids in leaf growth
  • Provides some of the micronutrients
  • Some flowering plants like roses, and vegetables like tomatoes, and peppers do well with higher magnesium sulfate levels
Epsom Salt, Source




Calcium Nitrate

Most Calcium Nitrate fertilizer is comprised of Nitrogen 15.5% [14.5% nitrate and 1.0% ammonium] and 19%. calcium. Nitrate nitrogen is directly available for plant uptake, for fast growth. It also improves plant uptake of the cations potassium, calcium, and magnesium. Calcium improves cell wall strength and optimum root environment. Cell wall strength, helps plants tolerate disease and tolerate heat stress.  It is recommended to be used with other balanced fertilizers. 

Calcium Nitrate
Calcium Nitrate, Source






A little about pH

pH-meter, Source


You can’t really talk about hydroponic nutrients without first making a brief mention of pH. In the case of a hydroponic nutrient solution, the pH is more about the water pH that makes up the solution used in the hydroponic system. The pH of a substance or solution refers to the measure of acidity or in other words the hydrogen-ion concentration.


It is this concentration that plays a critical role in hydroponic nutrients availability in plants. The pH is measured on a scale of 0 to 14 with 0 being most acidic, 7 being neutral pH while 14 is the most alkaline. This scale is logarithmic as each unit’s representation is in 10 folds which means that a small change in pH represents a much bigger change.


The recommended pH range for hydroponic vegetable nutrients is between 5.0 and 7.0. The alkalinity of the water in hydroponic systems is also critical as it is the measure of the capacity of the water to neutralize acidity. When the pH is outside the range of a particular plant it will cause “nutrient lockout” and the plants will be unable to uptake the nutrients in the water solution.


If the alkalinity level is low, the water will have a very low capacity for buffering. This means that depending on what is added to the water, the pH will automatically change. High alkalinity in the water also means that the water has a high pH. This means that some acidity can be introduced in order to neutralize the high pH.


Acids and bases will be added to balance the pH solution. It is important to balance your nutrient solution pH after adding nutrients to your solution.



Mixing all the Hydroponic Nutrients


5 Things to know before mix your Hydroponic nutrients.

  1. Safety
  2. What?
  3. Where?
  4. When?
  5. How?


1. Safety

Always wear PPE’s (personal protective equipment) when mixing any chemicals or handling your hydroponic nutrients. Safety glasses and gloves are a must. keep all wet or dry nutrients, acids, and bases away from pets and children at all times. Using lists on any accessible nutrient reservoirs is also essential.


2. What?

What ingredients? Use these three nutrient ingredients to regularly fertilize your system

  1. N-P-K Hydroponic Fertilizer
  2. Calcium nitrate
  3. Epsom salt (magnesium sulfate)


What type of fertilizer? You will need to choose between a wet or dry fertilizer. Wet is popular with hobbyists and home growers because it is easier to work with. Dry fertilizers are usually cheaper to purchase and ship but will require a bit more effort and some measuring tools.


What Ratio? Nutrient mixes come in dozens of different ratios. Different crops have different hydroponic nutrients demands and some crops have different nutrient demands over different times in their life cycle. You will need to read a few other articles about the types of plants you want to grow to answer this one. You may even want to make a few separate systems so that each can have its own pH and nutrient balance particular to those plants. Plus, if you make any mistakes you won’t sacrifice your entire crop! You can get the basic rundown on custom NPK mixes and pH levels per plant species by jumping off sections of our article on the best vegetables for indoor hydroponic gardens.


3. Where?

This one may seem silly but most novice nutrient mixers will mix their hydroponic nutrients directly into the main reservoir. It can be done this way but it is most beneficial to use a separate bucket or container to mix your solution, then pH balance it, and then introduce the solution to the main reservoir. You can even pre-mix some solution and keep it safe with a lid until you are ready to use it to top off your main reservoir every few days.


4. When?

You will fill your system reservoir with your premixed hydroponic nutrients solution upon the start-up of your system.  When to add more premixed will depend on what the EC or TDS measurement is. EC is the electrical conductivity of the level of salts in your solution and is a good indication of what the nutrient levels are. It is not a perfect measure and will not indicate any micronutrients or other imbalances. You should dump your reservoir and flush your system if you notice a major change that you cannot correct. It’s also a good habit to do this at least every few weeks. In some cases, you can add beneficial microorganisms to your water to extend your water change times. This is known in the industry as Bioponics


5. How?

How much to mix? You should follow the instructions on the back of your NPK Hydroponic Fertilizer bag. It will tell you how much fertilizer to mix with Epsom salt and Calcium Nitrate. Unless you are following a custom blend most mixes are 1:2:2.  1 part Epson salt, 2 parts NPK fertilizer, 2 parts Calcium Nitrate.


Masterblend mix instructions
Masterblend mix instructions, Source

First, you will need a few things.

  • 5 gal Mixing bucket, sump, or mixing tank
  • Scale ( if you are measuring by weight)
  • Measuring spoons ( if you are measuring by volume)
  • Electric mixer or mixing pump that will sit in the bottom of the sump or mixing tank…or a good strong stick!


How to actually mix?  Add the correct measurement of water according to your hydroponic fertilizer. Add the Epsom salt and NPK Fertilizer. Start to mix the ingredients. Always add Calcium nitrate last as it is not compatible with the other ingredients. Mix well for a few minutes. Getting good turbulence is important to dissolve the solids. Undissolved solids that end up in your main reservoir can throw your pH and EC levels off later as they dissolve. Add the mixed solution to your main reservoir. 


Example of a popular mix combination for Hydroponic Tomatoes

  • 4 gallons of water in a 5-gallon bucket
  • 6 grams or 1 tsp per gallon   – Epsom salt…so multiply your chosen measurement choice x 4 
  • 12 grams or 2 tsp per gallon – NPK fertilizer…so multiply your chosen measurement choice x 4 
  • 12 grams or 2 tsp per gallon – Calcium Nitrate…so multiply your chosen measurement choice x 4 


Just like cooking or baking, the more you do, the easier it gets.




Hydroponic Nutrients Interactions and Antagonism


Hydroponic nutrients for vegetable intake are at relatively the same level. When one of the hydroponic nutrients is in excess in the nutrient solution, the intake of the excess nutrient will be higher at the expense of other nutrients.


This phenomenon is known as nutrient antagonism. This means that you can either have just the right amount of nutrients in a plant or have nutrient deficiency based on the intake by the plant.


Take for example a nutrient solution of nitrogen and potassium that calls for 190ppm nitrogen and 205ppm potassium. In the event that potassium is added in excess, it will cause nutrient antagonism not just with nitrogen but with other nutrients too. This will lead to nitrogen deficiency in plants.





Common Hydroponic Nutrition Problems


Hydroponic systems are not as forgiving as soil-based mediums which means that any nutrients deficiencies manifest very quickly in the plants. This calls for regular monitoring as well as the right amount of nutrient composition to observe the symptoms that might suggest that the plants have some nutrient deficiency. Some of the most common symptoms in hydroponic plants include:


Soluble Salt Damage

Soluble salts damage is either caused by poor quality water, accumulation of salts in the solution, or alternative media, over-fertilization, and inadequate leaching. In hydroponic systems, fertilizers are salts that are heavily fertigated. This means that the water requires adequate leaching as soluble salts are likely to accumulate in the solution or alternative media.


Some of the visible symptoms of soluble salts damage in plants include wilting, dead leaf margins, dark leave foliage, and root death. Damage from soluble salts in plants is detectable by monitoring the electrical conductivity of the nutrient solution and can be leached with clear water to remedy the situation. What is important is that you first establish the source of the soluble salts.


Calcium Deficiency

Calcium deficiency is mainly caused by nutrient imbalance or under-fertilization. Low pH levels have also been known to cause calcium deficiency in hydroponic plants. Some other common causes of this problem are low airflow, poor moisture management, and high temperatures.


Calcium is one of the few mobile nutrients in plants. This mobility is in the fact that it moves in the plant through water-conducting tissues. Since both roots and leaves compete for water during plant growth, high temperatures are likely to trigger a higher transpiration rate which implies that more water is likely to move to the leaves. This causes calcium deficiency in the fruit of the plant.


A common symptom of calcium deficiency in a plant is brown leaf margins. As the problem escalates, you are likely to notice brown-dead spots on the leaves. You can detect calcium deficiency by conducting plant analysis.


Since one of the causes of calcium deficiency is under-fertilization, apply fertilizers to address the lack of calcium in the nutrient solution. Correcting the pH levels to be between 5.0 and 7.0 as well as improving airflow in greenhouses are also effective in addressing calcium deficiency.


Boron Toxicity

Boron toxicity occurs when you apply too much boron to the plants. Compared to other nutrients found in fertilizers, boron has the narrowest difference between toxicity and deficiency. What this means is that if you apply too much of it, it will cause toxicity while applying too little boron causes boron deficiency.


Boron toxicity requires that you check carefully the calculations of the fertilizers before applying them to the plants. There is also the possibility of boron being present in irrigation water. Common symptoms of boron toxicity in plants are reduced root growth and yellow dead spots on the leaf margins.


Constantly conducting plant analysis can help detect boron toxicity and knowing the source of the excess boron is an effective measure to address the problem.


Nitrogen Deficiency

In most cases, nitrogen deficiency is often caused by under-fertilization, excessive leaching or nutrient imbalance. When there is nitrogen deficiency in a plant, common signs include light-green foliage, yellow leaf margins, stunted growth of plants, and possible wilting.


Nitrogen deficiency is detectable by measuring the electrical conductivity of the nutrient solution to establish whether nitrogen levels are either too high or too low. To address this problem, always try and trace the source and remedy the situation. This might require you to add nitrogen to the nutrient solution or establish whether there is an antagonistic nutrient that is causing the deficiency.




Picture of Grammy


I'm Grammy to my grandkids and most of the authors here. My gardening career started when I was a child digging and planting in my neighbors garden in Florida. As a teenager I worked on one of the first organic farms and learned the many benefits of organic farming. As a young Mom I started dabbling in hydroponics and became hooked! My family and I learned from research and "Hard school of Knocks " ways to improve our crop growing techniques which I am willing to share with you.