Hydroponic pH Levels: Acidity Measurement and Adjustment

Today we’re going over hydroponic pH buffers. No, they’re not sexy or glamorous, but pH buffers play an extremely important role in your hydroponic plants’ development. Not only that, but a proper pH balance is vital to regular soil gardening as well.  If you can maintain pH levels in that sweet spot, your hydroponic plants will flourish. Plus it doesn’t hurt to have a little knowledge on the topic to impress your hydroponic buddies and to have a deeper understanding of your own hydroponic system. Without further ado, let’s get started.

What is pH anyway?

You may be familiar with some basics of pH and acidity. For instance, it’s pretty common knowledge that pure water has a pH of 7.0. This is what we’d call neutral. Solutions that have a pH below 7.0 are considered acidic while those above 7.0 are considered alkaline or basic. In chemistry, pH is a measurement of the hydrogen ion (H+) concentration of a solution. If your solution is high in H+ ions, the pH is lower, and if your solution is low in H+ ions, the pH is higher. In other words, there’s an inverse relationship between pH and hydrogen ions. Keep in mind there’s more to it than just what was covered above, and it can be a little confusing. I suggest checking out chemistry resources for those interested in greater detail. For now, we’ll leave it at that.

The Importance of pH Balance in Hydroponics

As far as hydroponic gardening goes, a solution’s acidity helps plants absorb essential nutrients and micro-nutrients that are key to healthy growth. All plants have an optimal pH level that will maximize absorption. The levels vary from one plant to the next, but an environment that is slightly acidic (within the 5.5-6.0 range) is typically ideal. As the pH of your nutrient solution begins surpassing 6.5 some of the nutrients will precipitate out and stick to the walls of your growing chambers and reservoir.

Once this happens, your plant will no longer be able to utilize those nutrients. Your hydroponic plants will suffer nutrient deficiencies and won’t reach their full growing potential. Take a look at the chart below for some commonly grown hydroponic plants and their corresponding ideal pH range. Take note hydroponic marijuana growers, cannabis has a very narrow ideal pH range, which means more frequent checking and adjusting.


Plant Type Ideal pH Range
Marijuana/Cannabis 5.5-5.8
Tomatoes 5.5-6.5
Strawberries 5.5-6.5
Garlic 6.0-6.5
Lettuce 6.0-6.5
Cucumbers 5.8-6.0
Chives 6.0-6.5
Jalapenos 6.0-6.5
Parsnip 6
Spinach 5.5-6.6


Monitoring pH Levels

Since pH plays such a vital role in the absorption of nutrients by your hydroponic plants, it’s important to keep an eye on the pH levels of your nutrient solution. Fortunately there are multiple ways to go about doing this depending on your budget and hydroponic garden size (and in my case, laziness).

Manual Testing

One common and inexpensive route to checking your solution’s pH level is through the use of paper test strips. These pH strips are covered in a dye that changes color when dipped in a solution. The color is then compared against a chart that explains which colors correspond to which pH levels. The main issue with pH strips is it can be difficult to get a precise reading on your solution’s pH. This may be acceptable for hobbyist hydroponic gardeners, but if you’re trying to optimize your yields, you’ll probably want an exact reading on your pH levels. While we don’t offer these through PonicShop, they’re extremely easy to find at local pharmacies, department stores, or home improvement stores.

Along with pH test strips, another common tool for monitoring acidity is with liquid pH test kits. Add a few drops of pH dye to a small amount of your nutrient solution, and compare the resulting color against an included pH chart. Liquid test kits are much more accurate and reliable than strips while also having a reasonable price tag. While we don’t offer individual liquid test kits here at PonicShop, we do have a handy kit courtesy of General Hydroponics, the General Hydroponic pH Control Kit. This kit includes the essentials for maintaining and testing pH levels, such as pH Up, pH Down, a sampling tube, and liquid pH tester.General Hydroponics pH Control Kit

Electronic Testing

If you’re a serious hobbyist or growing hydroponically on a large scale, it’s not feasible to test small samples of your solution on a regular basis. This is where digital pH meters come to the rescue. Digital meters are extremely fast, accurate, and convenient. Digital pH meters range enormously in size and price, however the most popular type of digital meter is the pH pen. Simply dip the pen into your nutrient solution and the LCD screen will read back the pH level for you.

PonicShop offers a variety of these digital meters. One extremely popular digital meter pen is the Bluelab pH Pen

Bluelab pH Pen

Most of these digital pens offer a warranty, which should give you peace of mind if you’re on the fence about spending a little extra for the convenience of a digital pH tester.

Higher-tech digital meters provide a multitude of measurement options beyond just pH. As an example, the Bluelab Combo Meter measures electrical conductivity and temperature along with pH. This post is aimed at pH, so we won’t go into the others too much. However EC measures the nutrient strength of a solution. This is another factor you’ll want to optimize, because too strong a nutrient concentration will cause root burn and too weak a nutrient concentration won’t provide your plants with enough nutrients to sustain their growth. And of course, water temperature is importantplants don’t grow in arctic or sizzling water.

There are a few caveats when it comes to digital meters. Because these meters are electronic, they require both calibration and maintenance. This amounts to keeping the measuring electrode clean and storing the meter’s tip in a solution recommended by the manufacturer.


Tweaking pH Levels

So how do you go about tweaking your pH levels once you’ve checked them? The two most popular options are phospohoric acid, which lowers pH, and potassium hydroxide, which raises pH. As is the case with most hydroponic chemicals, some caution needs to be exercised while handling these. Acidic and basic chemicals can cause burns and blindness if splashed in your eyes. At PonicShop we always advise the use of safety eye wear.

The consumer-grade pH adjustment chemicals are typically diluted to a safe level and are easy-to-use. Even with that being the case, small amounts of buffer can go a long way. Be sure to recheck your solution frequently as you add the buffer. If the pH level of your solution changes more than around 0.5 in the span of 12 hours this could shock your plants and would be an easily preventable way of killing your hard work.

The products available out there are usually aptly named pH Up or pH Down, so there’s no confusion when trying to adjust your solution’s pH. Popular name-brand liquid pH buffers that can be bought at PonicShop include:

General Hydroponics ph Up  and General Hydroponics pH Down

General Hydroponics pH Up, qtGeneral Hydroponics pH Down, qt

Technaflora pH Up and Technaflora pH Down

Technaflora pH Up, LTechnaflora pH Down, L

Botanicare ph Up

Botanicare pH Up, qt

Of course we offer several more brands that are just as effective. When it comes to pH buffers, which product you go with depends largely on personal preference for a specific brand.


Nutrients’ Role in pH

One thing to keep in mind when tweaking pH levels is that nutrients added to your solution generally lower the pH of the water due to the chemicals contained within the fertilizer. So ensure that you’ve already added your nutrients to your solution before checking and adjusting your pH. As your hydroponic plants use up the nutrients within your solution, pH will tend to rise. Thus we recommend checking pH regularly (about once a day). The rate at which pH is consumed is dependent on many different factors such as plant type, growing medium, and growing systems. As a side note, many users report that pH Down is used more frequently than pH Up because of the tendency for pH to drift up as nutrients are consumed. However…


Water’s Role in pH

Water is another major factor when it comes to your hydroponic solution’s pH. While this topic is worthy of its own separate article, I’ll just touch on some brief points.

Reverse osmosis (RO) water requires more pH Up than you’re used to when running a distilled water or tap water system. Distilled water is another commonly used water for hydroponics. Perfectly distilled water sits at a pH of 7, which is neutral. However distilled water comes with its own set of caveats, such as that your plants end up deficient in some key nutrients. Tap water, in the form of either hard water or soft water, varies in pH. Generally, hard water will run more basic (above a pH of 7.7), and soft water will run between 5.5 and 7.7. Knowing which type of water you’re running is a key aspect to keeping your pH levels balanced.

As you get a feel for the type of plants you’re growing, the water you’re running, and numerous other variables, you’ll know when it’s time to check and/or adjust pH.


Types of Hydroponic pH Buffers

When searching around for buffers that fit your needs, you may notice that both dry and liquid variants are available for purchase. The primary difference between the the two boils down to bang-for-your-buck and convenience. If you’re a small-time grower, a bag of dry pH Up could last you years. Chances are you’d rather have a bottle of liquid in this case. On the other hand, if you’re running a medium-to-large sized operation, dry buffer can make sense economically. Because dry powder is, well, dry, you get much more buffer for the same weight as a liquid variant, which reduces shipping costs. For those interested in giving dry powders a shot, one such product is General Hydroponics pH Up Dry. Unfortunately from what we’ve seen, General Hydroponics pH Up Dry is a seasonal item and is often difficult to obtain.General Hydroponics pH Up Dry, 2.2 lb

Worth mentioning is that there are several anecdotes out there that claim dry powder is weaker than liquid buffers. We can’t verify whether this is the case, but it’s something to keep in mind.



As you can see, the topic of pH as it pertains to hydroponic growing can get pretty intricate. After reading through this guide, you should have an alkaline (heh) understanding of acidity and why it’s important for your plants’ growth. Both monitoring and adjusting pH levels is something all new hydroponic growers need to get comfortable doing. There are, of course, several other factors beyond acidity that influence how your plants grow. Look forward to more guides in the future covering these topics.


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