The Best pH And EC Values For Hydro Marijuana Growers

living things on earth need water (H2O) to survive. Plants (just like humans) require water and are made up of about 2/3 water. It’s important to have a good understanding of the type of water that your plants receive in the same way that it’s important to know how different foods have different effects on our own bodies.

Water content is always different, so we’ve provided a few guidelines to understand how it’s used. For the growth of all life, the correct acidity of the growth medium, fertilizers and water is very important.

The acidity level determines the quality of the bacterial life, and the metabolic rate of the marijuana plant. Bacteria, which are important for the conversion of fertilizer to absorbable substances thrive best in a neutral environment, which means a pH level of 7. Learn what the best pH, EC/TDS levels are for hydro marijuana plants.

pH scale for cannabis plants

The pH is the rate of positively and negatively charged water ions, so in other words, it measures the absorption within a solution. You can figure out the acidity level by how many positively charged ions there are. If the negatively and positively charged molecules are at a balanced ratio, then the environment is considered neutral.

Depending on what materials are entered into the solution, the acidity level may become more alkaline or acidic. What determines the pH level is simply the absorption of positively charged ions in the solution (wikipedia).

The pH scale goes from 0 (acid) to14 (alkaline). For a solution to be neutral which means it is non-alkaline and non-acidic, it needs to be at pH level 7. This is a mathematical scale so with a consideration of 10, for every point that the pH level shifts the solution either increases in acidity or becomes more alkaline.

When you consider pH level 7, a liquid that has a pH level of 6 is literally 10 times higher in acidity. As for a pH 5 it would be one hundred times higher in acidity. Be very cautious when blending acids and salts because they easily become a lot quite fast.

The pH scale essentially measures the acidity and alkalinity levels in water. “pH” is an acronym for the potential (p) of the existence of the hydrogen ion (H+) in the water. The scale runs from 1 to 14, meaning that a pH of 7.0 has an equal balance between hydrogen ions (H+) and hydroxyl ions (OH-).

Use water with pH 5.8 for marijuana
Use water with pH 5.8

In some way or another cannabis plants require trace elements which are restricted to water that is high in pH levels and is not able to be taken in by the plant. Everything that is good for one part of your plant may not necessarily be good for another. For example the needs of trace elements and the roots differ, so you have to figure out a pH that works for every part. You are better off choosing water and nutrient liquids that are somewhat acidic with a pH around 5.5 – 6.5. You can adjust the levels to go up half a point.

You can think of pH like the hotness or coldness of your food. If your food is too hot, then you will burn your tongue or get heartburn. If it’s too cold, your teeth will hurt and you’ll get brain freeze. Finding the ideal pH balance is important for marijuana plants to absorb their food and have good health.

Hydro pH levels

  • Excellent – around 5.5-5.8
  • Good – around 5.3-6.5
  • Acceptable – around 5.0-7.0
  • Disturbed nutrient concentration – under 4.5 and  higher than 8.0
  • Permanent harm to the roots – under 3.5 and over 9.0

Hydro pH too low

If the pH level is 5 or beneath that, then it is clear that certain elements, especially aluminum are shifting to the point of where they are becoming toxic to your plant. You can stop this from happening by making sure the nutrient liquids stay at a pH of 5.5 or higher.

Always take a measurement of the pH of your nutrient water and make the necessary changes prior to feeding it to your plant. One way to raise the pH is by mixing caustic potash into the water, which you can find at a local garden center. More info in the article How to rinse your hydro growing medium

Hydro pH too high 

When you have a pH of 6.5 or higher, the calcium, iron and phosphorus ions are constrained to each other. Even though these elements are existing in the solution, they are not expendable. If ever you find this has happened the effects are a severe reduction in the progress of your marijuana plant.

The solution to a pH of 6.5 or above is adding a diluted nitric acid to the nutrient water during the growth stage. Once it reaches the flowering stage add diluted phosphoric acid to it. You can also find these in your local garden center labeled pH- growth and pH- flowering. Just make sure not to overdo it with adding this.

Once you have added something like pH+ or pH- you will need to measure the nutrient water to ensure the pH balance is right. Remember that if you end up raising the EC because of the acidity levels, it could easily result in a decrease in pH levels. Read the article How to rinse hydro growing medium for more information.

Cannabis Hydro EC and TDS values

EC stands for Electric Conductivity. You will want to provide your plant with a sufficient amount of nutrients for each stage and an EC meter is how you would determine the nutritional value. You  can also measure the amount of nutrients in TDS (Total Dissolved Solids).

You may find it hard to determine obvious values for the amount of nutrient salts in a solution. The EC will be affected by how big your plant is, how much water, the amount of time you drip, the lighting, the organic EC values of the tap water and the humidity levels in the environment.

Now you can always do things based on your own choices. There are growers who do well working with unusually high nutrient solutions while other growers get excellent results with a weaker solution. The best fertilizers for cannabis plants will most likely have an EC value of 1.2 till 1.5 mS (600 to 750 TDS), which can go as far as 3.0mS (1500 TDS)  if your plant is more matured. The EC will need to be changed if the EC of tap water varies a lot from that of various nutrient solutions averages.

Growing marijuana using hydroponics
Hydroponics Cannabis Growing

Let’s say grower 1 has tap water at an EC of 0.5 (250 TDS). This person may prefer the EC be 1.8 (900 TDS) and ends up adding a fertilizer that is at 1.3 (650 TDS).

And then we have grower 2 who has hard water and his tap water is at an EC of 0.8 (400TDS). The grower may prefer a 1.8 EC (900 TDS) as well, so he only needs to put 1.0 EC (500 TDS) amount of nutrients. This amounts to 0.3 EC (150 TDS) fewer than grower 1.

If grower 2 wants to have a similar proportion of fertilizer similar to grower 1, then he need to change the EC to 2.1. Your EC value will be influenced by the amount of drip feedings. So for instance, having a high solutions that is at 2.7 EC, spread over a period of 500 ml per plant is not as much of an issue as drip feedings of 150 ml with the exact solution, six times each day. Using the last situation, the salts end up releasing from the solution causing the EC to go up sky high.

The more you drip, the stronger your nutrients will be. Regardless you have to be aware of what each nutrient in the slabs does. Evaluate the EC and pH of the water that comes out of the slabs every two days. Use a syringe to get a sample of water from the slabs on each 5th and 6th day.

Download my free marijuana grow guide and find out more about how to keep pH and TDS levels well in control.

The plant may experience conditions throughout the scale that affect its ability to absorb certain nutrients. That’s why it’s very important to monitor the pH levels in the soil and the water so the roots and the plant itself remain healthy.

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Soil, hydroponics and aeroponics

The medium of soil acts as a buffer that can mitigate damage from any mistakes. That is to say, soil is much more forgiving for newbies. Of course, any damage that occurs with soil is much more difficult to fix. To avoid poor pH levels, mix a sample of your soil with distilled water, and then test the pH level of the water.

Hydroponic systems function by feeding all the nutrients a plant needs through mediums that are rather inert compared to soil. This effectively reduces the buffer zone that soil provides.

Cocos or rock-wool can still provide a small buffer that contains its own pH level. Of course, you should compensate for that by adjusting the nutrient solution.

Hydro vs soil method of growing weed
Hydro vs Soil

With aeroponics, there is no medium, which means there is no buffer. You won’t have to compensate for any medium so the nutrient solution in the water can be input directly.

It should be noted that the pH level of a nutrient solution is not always the same as the pH level at the plants’ roots. Look at the table to find compensation values for different mediums. pH, TDS/EC values are often contingent on temperature and time.

The primary food delivery system is water, and the plants use a process called “osmosis” to make it happen. The plants pull in nutrients through their roots and the nutrient levels are balanced in the water that’s in the plant and the water that’s around the roots. All the nutrients are absorbed through the external water, and the plant discharges waste (salts). Plants use the same “don’t-shit-where-you-eat” logic that we do, meaning that it’s important to understand how many and what nutrients are in the water.

TDS and EC

Inexpensive pH meters can be found at most garden centers, grow shops, and pond stores. You can measure the concentration of ionic salts in the water with two different scales:

  • Total Dissolved Solids (TDS) measured in  Parts Per Million (PPM)
  • Electrical Conductivity (EC)

Water that is pure H2O will not efficiently conduct electricity, but most tap water will contain necessary ions (H+ and Cl-) for conducting electricity. More ions will result in better conductivity. We use this relationship to determine how many nutrients (salts) are in the water.

Plants require diets that are as diverse as diets for people. Some plants may need larger meals that offer more nutrients for growing. By contrast, other plants might be “drowned” by too many nutrients and would require smaller meals. The best TDS values will differ depending on the foods provided and the plants themselves.

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Feeding the marijuana plants

Soil For the most part, the pH balance is more important to soil growers than TDS/EC values (although an TDS meter is always a good investment). You can monitor the soil using only pH and staying within the recommended range.

That being said, some nutrients are absorbed more fluidly at different pH levels. The graph illustrates the ideal pH values to optimize nutrient absorption. For instance, nitrogen (N) absorbs better at pH 6.0, while phosphorous (P) and potassium (K) are better at 6.25 and up. This may necessitate a change in pH values when you shift from vegetative state to flowering.

Quick Tip: Always prepare the formula before measuring and changing the pH when you’re mixing a nutrient solution.

Hydro-, Aero- Because hydro- and aero- mediums limit the effect of the buffer, it’s important to focus on TDS/EC, and pH. Nutrients can be absorbed more easily at different TDS values. Hydro- and aero- mediums use direct feeding, which means that you have to carefully ensure that the plants won’t starve while also making sure that they don’t receive too many nutrients which can restrict absorption.

EC Meter for water checking
EC Meter

If you’re using reservoir or re-circulatory water systems, then certain cleansing methods like reverse osmosis can drastically improve water quality. It effectively filters out surplus salt build-ups, ensuring that growers will be able to maintain their water quality and support the absorption of nutrients. All of this is sure to provide maximized results.

In the end, making sure that your water quality is high requires some work, but it’s important to achieve a successful product. Next week I’ll upload some example feeding schedules and show you how to mix and level your water. Download my free grow guide and order some high quality marijuana seeds at this link here. We ship seeds to the US, CA and many other countries.

For any growing related question please visit the marijuana support page.


Avatar for Robert Bergman

Mr Robert Bergman PhD


Robert Bergman is an Amsterdam-based marijuana grow expert who has years of experience from small grows to massive operations ... See profile

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12 comments on “The Best pH And EC Values For Hydro Marijuana Growers”

  1. steven,

    Yes, you can start your seeds in seed starting mix.

    I suggest you look around our forum and choose what you will be using before you get started.

    We have many helpful growers and staff alike that can help you get on track, and grow successfully. 😉

  2. hey mr. bergman i just got my seeds.i pickd up a bag of Miracle gro seed starting poting mix would u recamend this for starting my plants?

  3. Ruth,

    Most of the information here is based on controlled grows, and can be interpreted may ways.

    It is best if you follow these guidelines and learn by watching how your plant responds.

    I think it would be safe to use this formula for auto flowers. I also would recommend you allow yourself to vary up to 25% +/- if you need to.

  4. bud,

    That depends on how hard water is. my well is 220 ppm, and 7,2 PH You can basically grow anything with that even though PH is a bit alkaline. You can also buy nutrients for hard water from some nutrient companies.

    Join our forum for a more in depth conversation. Ask for Dumme or latewood. Happy growing

  5. Hi, I advise you to join the support forum. You can post pictures there and you will get a faster response from our expert growers; Especially in an emergency!