Why is pH Important for Hydroponics?


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pH is important in hydroponics because plants grown in hydroponic systems require different pH levels than plants grown in soil. Getting the right level of pH is vital as it affects nutrient availability and plant growth. 

Hydroponic cultivation allows you to grow anywhere, produce higher yields, control the conditions, and fewer resources are needed, thus reducing costs.  Optimal pH (potential of hydrogen) levels in hydroponic cultivation systems are important for hydroponic growers to understand nutrient availability, water hardness, and prevent deficiencies. 

When people want to grow plants and produce, more people are turning to hydroponic cultivation methods. But when it comes to the importance of pH and optimal levels, it is usually not fully understood. 

Hydroponics is a fantastic way to grow plants which can be narrowed down into six types. It is a form of horticulture (cultivating plants for either food or ornamental purposes) and a subclass of hydroculture (growing plants in an aquatic-based or soilless environment) where mineral nutrient solutions in an aqueous solvent are used. To put it simply, it is soilless gardening!

If you are one of those hydro-curious people or are already a hydroponics expert, this article is going to explain everything you need to know regarding pH and why it plays such an important role in hydroponic systems. 

The Importance of pH in Hydroponic Systems

In hydroponic systems, pH levels are extremely complex because of microbial activity, fungal development, access to nutrients, and root growth. 

pH is one, if not the most important water quality factor in hydroponic systems and cultivating plants. Plants grown in hydroponic systems require different pH levels than plants grown in soil. Plants cannot absorb nutrients when the pH levels are too high or low, so monitoring and maintaining the pH levels are vital for hydroponically grown plants.

When plants grow in the wild, nutrients and inorganic and organic compounds are absorbed from the surrounding environment. These plants have learned to utilize the natural fluctuations of pH in soil substrates. 

Hydroponic cultivation systems are soilless, so plants cannot benefit from nutrient cycles and microbial interactions that occur naturally in soil. As a hydroponic grower, you are responsible for creating an ideal growing environment which comes down to you monitoring and adjusting pH levels to ensure nutrients are readily available. 

pH for Hydroponics 

When we talk about pH in hydroponics and optimal pH levels there are many terms you are likely to stumble upon which can get a little confusing and often overlooked. To understand why pH plays a vital role in hydroponics, we have to dip into chemistry a bit…

pH is a logarithmic scale that ranges from 0 to 14, 7 being neutral, <7.0 acidic, and >7.0 is alkaline or indicates a base. pH is how we measure how acidic or alkaline an aqueous solution is. 

We all learned in school that water consists of hydrogen and oxygen; two hydrogen atoms and one oxygen atom. When solutions mix with water, these atoms are broken up, it is this process that determines whether a solution is acidic or alkaline. The pH scale relates to the concentration of hydrogen or hydroxide ions formed in a solution. 

So, what does this mean for cultivating using a hydroponic system? 

The pH scale tells us about nutrient availability, water hardness, and understand deficiencies. When pH levels drop below 5.5, it can cause copper and iron toxicity or magnesium and calcium deficiencies, and pH levels above 6.5 cause iron deficiencies. 

Common Nutrient Deficiencies

Nutrient deficiencies are related to pH levels and are something you want to avoid as they can result in plant death. 

Below are common signs of nutrient deficiencies in plants:

  • Iron: Pale/yellow leaves
  • Calcium: Burnt tips & leaf cupping 
  • Magnesium: Yellowing between leaf veins

It is the importance of pH in such systems that reverse osmosis (RO) is used. RO is used in hydroponic systems to remove mineral content and figure out the buffering capacity of water, which we will get into later on in this article. 

Nutrient Availability, Buffering Capacity & Optimal pH Levels

Nutrient availability in hydroponic systems generally occurs at a pH between 5.5 and 6.5, however, these ranges may vary between what you are cultivating. 

pH ranges are important to know as some nutrients are unavailable to plants, so even adding them to your plants becomes a waste of time; the plants cannot utilize them. 

To understand nutrient availability, we can use iron (Fe) as an example. Iron is an essential micronutrient for plants, playing a crucial role in their metabolic processes (DNA synthesis, respiration, and of course, photosynthesis). Iron also plays a major role in chlorophyll synthesis, maintaining the function of chloroplast structure. 

Iron incomes in two forms:

  • Ferric (+3 charge): Unavailable to plants
  • Ferrous (+2 charge): Available to plants 

In hydroponic systems, fluctuations between the two can occur. When ferrous iron is converted into ferric it can cause iron deficiencies due to pH levels increasing. That is why hydroponic nutrients are added to reduce the pH level and allow plants to thrive. 

A buffering capacity is the capability to prevent changes in pH. Water used in hydroponic systems is usually full of carbonates, making the water hard. It is important to test the pH as carbonates in water increase the buffering capacity. If this is a frequent issue, using an RO filter will become your best friend. 

pH & Perfect Growing Conditions 

Plants and crops require different pH ranges, therefore it is recommended to group plants that have similar pH requirements and refer to pH charts. To help you out, we have put together a table of common plants and crops that are cultivated using hydroponic systems and their pH ranges.

Plant/CropIdeal pH Range
Lettuce 6.2-6.8
Tomatoes 5.5-6.5
Strawberries 5.5-6.5

It is important to also consider the electrical conductivity (EC) of your hydroponic solution. The pH requirements of plants and the EC interact with each other. When a high EC is measured, this means more nutrients are dissolved in the solution, playing an important role in the plant’s growth. 

What Causes pH Fluctuations In Hydroponic Systems?

Many factors can influence pH levels in hydroponic systems to change, but the main issue is nutrient and water uptake from the plants. Having a large reservoir and constantly topping it up can prevent this. 

Another factor is when the growing media buffers the pH. Inorganic media can change pH levels, so to tackle the issue, dip the inorganic media in weak acid which allows the media to neutralize the acid. 

pH fluctuations can also come from organic properties such as bacteria and algae. Keeping the solution slightly acidic, observing root health, and disposing of decayed roots should combat this issue. 

How to Adjust & Test pH Levels in Hydroponic Systems?

Adjusting pH levels gives you control over your reservoir. Whenever nutrients are added pH levels must be tested to check they are within the general pH range (5.5-6.5). High carbonate water is resistant to pH changes, so you may need to increase or decrease the pH levels. 

pH can be adjusted either manually or automatically with the use of a pH dosing pump. This allows continuous and automatic pH control in the hydroponic system. To stabilize pH levels in nutrient-rich waters, acidic or basic compounds can be added. 

Decreasing the pH

To decrease the pH level, you will need to add acid to the nutrient solution. It is important to use an acid that is safe for plants and for you to handle. Hydroponic growers tend to use a 2-5% phosphoric acid solution.

Increasing the pH

To increase the pH level, an alkali can be added to the nutrient solution. The use of potassium hydroxide is the go-to solution as it also supplies the plant with potassium which regulates water vapor, oxygen, and carbon dioxide exchange. 

Testing pH

By now you should be well aware that pH is important in hydroponics. The first step to maintain pH levels is through consistent pH testing using pH meters (metal-electrodes, glass-electrodes & semiconductor sensors), pH indicators, or pH litmus test paper. 

We recommend using a pH kit or hydroponics kit. A hydroponics kit measures pH, conductivity, and temperature all in one! When using any measuring equipment, always calibrate before use to ensure you get accurate readings. 

Summing Up pH In Hydroponics & Optimal pH Levels

Hydroponics is soilless gardening and is a fantastic way to grow plants as you can grow anywhere, produce higher yields, control the conditions, and fewer resources are needed. 

To be a successful hydroponic grower you must understand the importance of pH and be able to cater to the plants’ different needs; this is a key component to hydroponic cultivation success.

Nutrient availability in hydroponic systems generally occurs at a pH between 5.5 and 6.5, however, these optimal pH ranges may vary between plants, so always research plant-specific requirements. 

Our goal is to help make hydroponics easy and accessible for you. If you have any questions regarding hydroponics, pH, or the products we have to offer, please feel free to reach out to our world-class team at Atlas Scientific.

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