Garden & Greenhouse


Is the pH of a Hydroponic Solution Really That Important?

Posted September 25th, 2015 by Garden & Greenhouse in ,

The correct pH is only important if you want healthy plants, otherwise you don’t need to worry about it. Plants can suffer from nutrient deficiencies, even with a fresh and perfectly balanced nutrient solution if the pH is out of range. It is kind of like how you can freeze to death in full sunlight at the North Pole, or drink all the salty seawater you want and still suffer or even die of dehydration. Even when one growing variable is sufficient, another variable can cause a big problem. Think of it like being really hungry, and there’s a nice big juicy hamburger just out of reach.

Improper pH ranges can also result in precipitates (calcium sulfate), a white cloudy or powdery looking substance that can float or even settle at the bottom of your reservoir. When the pH of the nutrient solution rises above 7.0, a chemical reaction can occur causing the calcium to bond with sulfate and other trace elements like iron, copper, zinc and manganese causing them to become unavailable to the roots.

It can even cause problems with emitters and/or misters clogging, and buildup in the growing medium, and in extreme cases can cause plumbing blockages or restrictions (like clogged arteries). The exact pH where the precipitation of the nutrients begins depends on the concentrations of calcium and sulfate in the nutrient solution. But it typically can begin at 6.5, unless the particular nutrient solution is low in concentrations of calcium and/or sulfate. Generally speaking, higher nutrient concentrations are more likely to result in precipitates, than lower concentrations.

When to Check the pH of Your Nutrient Solution

For the best results it’s a good idea to have a regular routine for checking your pH levels and adjusting them when necessary. Check the pH of the water before initially adding the nutrients to help prevent precipitates while mixing them up. But unless the pH is well above 7.0, don’t bother trying to adjust it before adding the nutrients or you may experience wild pH swings while trying to reach the target pH.

Most nutrients have pH buffers added, and will begin lowering the pH as soon as it’s added if it’s too high. If the nutrients that you are using have more than one part, add them separately and thoroughly mix each of them before adding the next part. The same practice should be used any additives that you may be using. Check the pH of the freshly mixed nutrient solution once it’s all mixed and ready to use.

You should also check the pH of any system other than a non-recovery (run to waste) system daily, because the nutrients and water the plants take up causes the pH to change, particularly when the water to plant ratio is low. In other words, the larger the amount of nutrient solution, the less fluctuation that is likely to occur, and larger plants use more water and nutrients than smaller plants. You should also check the pH anytime you add any fresh water to top off the reservoir (and/or nutrients or additives). The pH of the water supply can change daily, so even if you have checked it in the past, it can be different today.

Checking and Adjusting the pH

To check pH you can use a liquid pH indicator (drops), paper test strips, or an electronic pH meter. The electronic testing meters are the most expensive option and require calibration (including calibration fluid), as well as regular maintenance and care or they won’t give accurate results.

If you use one, follow the manufactures instructions carefully, but even with proper care and maintenance, they may not give reliable readings. I prefer to use the liquid pH drops because they are inexpensive, as well as accurate, and cost less than the calibration liquid for the electronic meters. But the main reason is they don’t require any calibration or maintenance in order to be accurate and reliable. I have never used the paper test strips, but they don’t require any calibration or maintenance are quite accurate as well.

Choose a target pH, for your nutrient solutions. It’s completely unnecessary to hold pH at a single point value like 5.8, in fact it’s better not to. Plants have evolved over millions of years and can easily tolerate pH ranges, and the less pH adjusters that you add to your nutrient solutions the better. Choosing a target pH right in the middle of the range you intend, allows for pH fluctuations in either direction. A good example would be if the pH range for the plants you are growing is 5.5 to 6.5, set the target pH for 6.0 which gives room for fluctuation in either direction.

pH Adjusters (pH up, and pH down)

pH adjusters come in dry and liquid forms. Whichever you type you use, make sure to add small amounts at a time. It’s impossible for manufactures to give exact directions on how much to add because of all the variables like the size of reservoir, type of nutrients, whether the nutrients have pH buffers added and the amount of pH change needed. When you are adding pH adjusters, it’s best to dilute them in water before adding it directly to the reservoir. This helps prevent precipitates from extreme pH changes before they can be mixed in. If the pH is accidentally raised above 6.5, lower it again as quickly as possible.

Jeff Sanders runs a hydroponics website call to help hydroponics enthusiast learn how to build their own hydroponic systems, as well as learn about many topics related to hydroponics so they can grow to their own crops successfully. He is a hydroponic gardener and enthusiast with over 7 years of experience growing hydroponically. He is currently building a small commercial hydroponic greenhouse to grow fresh herbs. You can contact him through his website and at

Want more information? Read these articles:

Are Your Plants Hungry? The Importance of Understanding pH

How to Assess and Correct Soil pH

pH Testing in Hydroponics Explained

pH? Widely Used, Little Understood

The Importance of pH in Horticulture

The Role of pH in the Garden

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