The main hydroponic nutrients include nitrogen, phosphorous, potassium, calcium, and magnesium. Hydroponic plants need more nitrogen fertilizer than traditionally grown plants because soil is rich with nitrogen. The NPK ratio refers to the ratio between nitrogen (N), phosphorous (P), and potassium (K). 

The Basics Of Hydroponic Nutrients

Healthy, happy plants require nutrients. Just like each plant is different, so are the nutrient requirements of each species.

Because hydroponic systems don’t utilize soil, you need to deliver the plants’ nutrients through a nutrient solution. Your plants will only receive the minerals and vitamins that you purposefully give them. 

Therefore, it’s up to you to know what the right solutions are, for the right plant, at the correct stage of growth.

Key Nutrients for Plants

Let’s go over the five key hydroponic nutrients for plants. If your nutrient is 90% soluble, that means that 90% of the product will dissolve in water.


Nitrogen is used by plants for typical leaf and stalk growth. It’s a major player in chlorophyll. Chlorophyll lets plants turn sunlight into much-needed energy through photosynthesis.

In addition, nitrogen helps to build amino acids that create proteins for your plants. 

If your plants don’t have nitrogen, they won’t have a stem structure and they won’t be able to properly photosynthesize.


Phosphorous is vital for root systems and the creation of seeds. It also helps build plant tissue for things like flowers and buds. Likewise, it helps your plants fend against diseases and pests.

Without phosphorous, your plants may not flower.


Potassium helps your plants regulate their CO2 intake during photosynthesis. Photosynthesis can’t take place without CO2. Potassium also helps your plants regulate water levels and utilize growth enzymes.  

Low potassium levels slow down plant growth.


Calcium is a major component of the cell wall. Strong cell walls strengthen and develop tissues quickly. Calcium also lets water and nutrients penetrate your plant better.

A lack of calcium can cause your plants to wither and brown because the cell structure gets damaged.


Magnesium helps your plants intake phosphorous, assisting photosynthesis. It’s also a major building block of chlorophyll, which makes plants appear green. 

If your plants are low on magnesium, their growth will slow down and their color will fade.

Choosing the best fertilizer for your crops

Liquid fertilizer mixing in bucket for growing

When you’re searching for the right hydroponic nutrients, it’s important to be sure that the solution is specifically designed to be used in a hydroponic system. DO NOT buy nutrients designed for soil.

Soil has its own special makeup so the nutrient needs of soil is quite different than the nutrient needs of a hydroponic system.

A good hydroponic fertilizer will have all of the hydroponic plant nutrients you need for growing without soil. To demonstrate, soil has a lot of nitrogen, so if you get a nutrient solution designed for soil it won’t have much nitrogen in it. 

Meanwhile, hydroponic systems need nitrogen to be in its nitrate form because there’s no soil. 

The NPK Ratio

The NPK Ratio is the ratio of nitrogen (N), phosphorous (P), and potassium (K).

The packaging on your nutrient solution will almost always show the NPK ratio as three numbers with dashes in between them, such as 5-4-4. Each number is the percentage of the nutrient that’s in the solution.

So a 5-4-4 NPK ratio means your hydroponic fertilizer has 5% nitrogen, 4% phosphorous, and 4% potassium. 

Each plant has different NPK needs for optimal nutrient ratios. The optimal nutrient ratios also change between different stages of growth.

Synthetic vs Organic Nutrient Solution

If you have the option, you should always choose organic nutrient solutions for hydroponics. Organic nutrient solutions are made out of natural, organic materials like fish emulsion and bone meal. 

Meanwhile, synthetic nutrient solutions are made out of lab-made chemicals like sulfates and phosphates. 

While both synthetic and organic nutrient solutions have the same amount of nutrients, organic nutrient solutions are better for both your plants and for your health. They’re also almost always high-quality nutrients for hydroponics.

Certain hydroponic gardeners prefer synthetic solutions since they don’t tend to clog up hydroponic pumps the same way that organic solutions tend to. Synthetic nutrient solutions are pre-broken down, so they travel through the system more easily and release quicker. 

Organic solutions have a slower release and require a bit more care, but are definitely worth the extra work.

Fertilizer Form      

You can get your hydroponic nutrient solution as two types of nutrients: liquid nutrients or hydroponic powder nutrients. You can use either as long as they have the nutrient ratios you’re looking for. It comes down to personal preference, convenience, and cost.

Liquid fertilizers tend to be used by hobbyists and growers that work on a small scale. They cost a little more, but they’re already mixed and very easy to use.

Dry fertilizers are usually reserved for large commercial growers. The minerals need to be both mixed and diluted. They cost less when you buy them in bulk.

To mix your hydroponic nutrients, most people use a mixing tank or a sump because it has turbulence. This gives your hydroponic nutrients space and turbulence so they can mix all the way. You can choose the spot in your system where this will work best.

You can mix your nutrients for hydroponics separately and then combine them, or you can add them to your tank one by one.

Monitoring pH and EC Stability

Digital pH meter tester Hydroponics

Your pH measures how acidic or alkaline your substrate is. When you regulate it properly, it lets the roots suck up the right volume of nutrients for optimum plant health. 

Hydroponic systems have more acidic substrates than traditional soil. The nutrient solutions and fertilizers also tend to be more acidic.

The main factor to cultivate successfully is to maintain the pH value of your solution consistent. The best solution pH for hydroponics is somewhere within the 5.5 and 6.5 range. An optimal number is 5.8. 

Investing in a pH meter is definitely worth it. If your pH is off, there are solutions that can raise or lower the pH of your water.

EC, or electroconductivity, measures the amount of mineral salts that are dissolved in your water. The EC needs to increase when your plants need more hydroponic nutrients.

An EC that’s too high indicates that there are too many nutrient salts in your plants’ roots. If this happens, you need to improve the drainage and regulate your nutrient solution. For example, you can dilute the solution with osmosis water instead of using tap water.

The EC should range from 1.2-2.0. The EC depends on both the fertilizer and the plants’ needs. Start at 1.2 and raise the EC over time.

How to Safely Dispose of Your Hydroponic Chemicals

First, let’s start with how NOT to dispose of your hydroponic nutrients.

Don’t just dump your hydroponic chemicals into your garden or down the drain. All the nutrients in your hydroponic water can be hazardous.

To illustrate, nitrogen pollution can cause major problems for local ecosystems. Too much nitrogen can lead to algae blooms.

In addition, many cities and counties have strict wastewater rules.

Here’s how to safely dispose of your hydroponic chemicals:

1. Mix your wastewater with tap water at a 1:1 ratio.

2. Use the resulting mixture to water your potted plants. Only pour into potted plants to avoid runoff.

3. The rest of the wastewater can be put down a bathroom or kitchen drain. These drains are meant to handle and process corrosive liquids, so they do a better job at taking care of your chemicals than if you just dump them outside.


Nutrients for hydroponic plants aren’t as scary as they seem. Armed with knowledge, you can pick out the right hydroponic nutrients and your plants will thrive.

Conduct some research for your specific plants to see what they like and need. This may differ between growth stages as well. 

Paying attention to NPK, EC, and more will help guide you on your hydroponic nutrient journey.