hydro ppm ph autoflower

Best pH Levels For Growing Autoflowering Cannabis

The way that Cannabis plants can utilize available nutrients will be down to the pH of the water. Understanding what pH means, how important it is and the role it plays on how nutrients are used can give you the upper hand when it comes to watering and feeding your garden. In this article, we explain about potential hydrogen, how it affects nutrient balance, and what to consider.

1. The Meaning of pH

The abbreviation pH stands for potential hydrogen, which is a value to indicate how much water and oxygen are present in a water source or nutrient solution. It is also an indication of how acidic or alkaline the water is, which ultimately has a major impact on how Cannabis plants uptake available nutrients.

2. Nutrient Availability and Uptake In Organic Mediums

When growing Cannabis in soil, the optimum pH level should be between 6.0 – 7.0. Organic growing mediums allow for nutrients to buffer over a 72-hour period, and once buffered will be more readily available to the roots at an optimum range.

Primary nutrients, secondary nutrients, and trace elements will be most available at pH 6.5. However, a grower should be expected to level pH levels naturally drift from one side to the other, in order for a plant to use exactly what it needs, without being restricted to a specific number. Once a solution passes pH 5.5, then the uptake of primary nutrients will be minimal, which can cause a chain of plant deficiencies to occur.

What To Remember

• Organic mediums will provide a natural buffering zone for 72 hours.

• Soil depends on the pH of the water or nutrient solution to drift between 6.0-7.0

• Below pH 5.5 primary nutrients can be accessed.

3. Nutrient Availability and Uptake With Hydroponics

Unlike organic growing that allows a natural buffering cycle, in combination with beneficial bacteria and fungi, hydroponic systems are far less forgiving. Using growing mediums such as rockwool, hydroton, perlite, and coco, the plant’s ability to buffer nutrients must be down to the careful work of the grower.

When growing with hydroponic methods, the optimum pH range for nutrient uptake and availability will be between 5.5-6.5. Depending on the various types of hydroponic farming, some systems may use a recirculating reservoir and others use a drip to waste method. As Cannabis plants are fed more frequently with small-sized minerals, the requirement to have the pH set to the ideal range, in conjunction with E.C levels is very important.

What To Remember

• Hydroponics has no buffering zone so the pH must be the ideal range.

• It is best to work between pH 5.5-6.5 allowing plants to drift.

• E.C should also be considered when using hydroponics or aeroponics.

• Using air stones for dissolved oxygen will increase pH levels over time.

4. How To Check Your pH

There are many variables that can cause pH to differ, so having the right equipment to measure is important. A very basic method is to use a pH test kit, in the same way, you would test the water quality of a swimming pool after using chlorine. These simple kits require adding 2 drops of solution to your water sample, then once diluted, the color of the sample will give a close estimate to the pH value.

A more professional approach would be to invest in a pH pen. These can be found in grow shops or aquarium stores and will give you an accurate digital reading each time you enter the pen into the water or nutrient solution.

If you are growing with organics or hydroponics, it is well recommended to check the pH of your tap water, or rainwater being used. Some water sources may need treating with acid or alkaline to increase or decrease pH levels before it is classed as suitable for plants.

Points To Consider

• Make sure that your E.C and pH pen are calibrated before using.

• Always check the water source you are using before adding nutrients.

• Testing the runoff from the base of your pots will indicate the pH level of the soil.

5. How To Adjust pH

When growing Cannabis there may be several times that you need to adjust the pH of your water source, or nutrient solution. The way that this can be done is to use an acidic or alkaline base, which is more popular as the products “pH Up” and “pH Down”.

If you are going to add either one, it is advised to do so at the very end of making your nutrient solution. This will allow you to only adjust the pH scale once, however, very small amounts are required and this balancing act will take time especially if you are using hydroponics.

6. In Conclusion

You may not realize how important pH is when growing Cannabis, and how too much of a severe drift to one side of the pH scale can affect the uptake and availability of nutrients. Making sure you have the right tools to monitor your pH levels will give you an advantage when feeding your autoflowering Cannabis plants, and can be the difference point between nutrient lockout and deficiencies.

The way that Cannabis plants can utilize available nutrients will be down to the pH of the water. Understanding what pH means, how important it is and the role

Cannabis & Water Quality Part 2: PPM & EC

Getting to grips with water quality is a factor that can distinguish between a novice and a veteran hobby cannabis grower. Here is part two of our guide, focusing on PPM and the EC of your water.


Water is a foundation of life. This is no less true for cannabis, which relies on water for a whole array of functions. In our previous blog on water quality, we assessed why water is important, and how pH can affect many aspects of your grow. Today we are going into a bit more detail with ppm and EC. Both are more advanced aspects of cannabis growing that need to be taken into account, and getting your head around it will help push your skills to the max. For the novice, while important, this information is not essential to grow. It is still possible to get great results without it, but it will certainly help!


To understand the nutrient concentration of your soil, you’ll want to test both the pH and PPM or EC of your runoff.


PPM is a measurement that gives you an indication of the amount of nutrients present in your growing medium. This is super important as it guides your next feed and allows you to avoid over- or underfeeding your plants. Measuring PPM is simple and can be done using most pH meters.


EC, or electrical conductivity, is another measurement that helps us determine the amount of nutrients present in the growing medium. The more nutrients in the medium, the higher the EC reading of your runoff. Measuring EC is simple with our DiST 4 Pocket Conductivity Tester by Hanna Instruments. Remember to measure your runoff regularly to know when to feed your plants, and how much to feed them.


For a clear picture of how much nutrients your plants are getting, you need to measure the PPM or EC of both your nutrient solution/reservoir (if you’re using hydroponics) and your runoff. Ideally, the PPM or EC reading of your runoff should always be lower, which shows your plants are taking up nutrients when you feed them. If your PPM/EC readings are super low in your runoff, it’s a sign you need to up your nutrients.

If there is no change in PPM/EC between your nutrients and runoff, this means your plants aren’t taking up nutrients properly. This is usually caused by spikes or drops in pH.

If the PPM/EC reading is higher in your runoff than in your nutrient solution, you’ll likely be dealing with salt buildup around the roots. As you feed your plants, this buildup slowly dissolves back into your runoff, driving up your PPM/EC readings. To deal with this, you’ll want to use an enzymatic line cleaner to clean your plants’ roots. Line cleaners remove any kind of nutrient buildup and can be mixed right into their water. Alternatively, you can also use filtered, pH-neutral water to flush your roots. Just keep in mind that this process takes multiple attempts.

PPM (Hannah) EC (mS/cm2) PPM (Hannah) EC (mS/cm2)
Early Growth 350 – 400 ppm 0,7 – 0,8 400 – 500 ppm 0,8 – 1
Seedling 400 – 500 ppm 1 – 1,2 500 – 600 ppm 1 – 1,3
Transition 550 – 650 ppm 1,3 – 1,5 600 – 750 ppm 1,2 – 1,5
Vegetative Stage 650 – 750 ppm 1,6 – 1,7 800 – 850 ppm 1,6 – 1,7
Vegetative Stage 750 – 800 ppm 1,7 – 1,8 850 – 900 ppm 1,7 – 1,8
Vegetative Stage 850 – 900 ppm 1,8 – 1,9 900 – 950 ppm 1,8 – 1,9
Flowering Stage 900 – 950 ppm 1,9 – 2 950 – 1000 ppm 1,9 – 2
Flowering Stage 950 – 1050 ppm 2 – 2,2 1000 – 1050 ppm 2 – 2,1
Flowering Stage 1050 – 1100 ppm 2,2 – 2,3 1050 – 1100 ppm 2,1 – 2,2
Flowering Stage 1100 – 1150 ppm 2,3 – 2,4 1100 – 1150 ppm 2,2 – 2,3
Flushing 0 – 400 ppm 0 – 0,8 0 – 400 ppm 0 – 0,8
PPM (Hannah) EC (mS/cm2)
Early Growth 350 – 400 ppm 0,7 – 0,8
Seedling 400 – 500 ppm 1 – 1,2
Transition 550 – 650 ppm 1,3 – 1,5
Vegetative Stage 650 – 750 ppm 1,6 – 1,7
Vegetative Stage 750 – 800 ppm 1,7 – 1,8
Vegetative Stage 850 – 900 ppm 1,8 – 1,9
Flowering Stage 900 – 950 ppm 1,9 – 2
Flowering Stage 950 – 1050 ppm 2 – 2,2
Flowering Stage 1050 – 1100 ppm 2,2 – 2,3
Flowering Stage 1100 – 1150 ppm 2,3 – 2,4
Flushing 0 – 400 ppm 0 – 0,8
PPM (Hannah) EC (mS/cm2)
Early Growth 400 – 500 ppm 0,8 – 1
Seedling 500 – 600 ppm 1 – 1,3
Transition 600 – 750 ppm 1,2 – 1,5
Vegetative Stage 800 – 850 ppm 1,6 – 1,7
Vegetative Stage 850 – 900 ppm 1,7 – 1,8
Vegetative Stage 900 – 950 ppm 1,8 – 1,9
Flowering Stage 950 – 1000 ppm 1,9 – 2
Flowering Stage 1000 – 1050 ppm 2 – 2,1
Flowering Stage 1050 – 1100 ppm 2,1 – 2,2
Flowering Stage 1100 – 1150 ppm 2,2 – 2,3
Flushing 0 – 400 ppm 0 – 0,8


Knowing your PPM helps you avoid possible burning by letting you know when to adjust the amount of nutrient minerals you add to your water. Cannabis enjoys 500-600 ppm after cloning, 800-900 ppm when vegetating, and 1000-1100 ppm when flowering. So knowing the mineral content of your water before mixing your nutes can avoid stressing you and your plants. For DWC (hydroponic) growers, it is important to know the condition of the reservoir water, as minerals can deplete as the water level drops – it is a heads-up for you to just top things up as required.

There are many probes, devices and metres on the market all able to measure ppm. The most common is a TDS metre (total dissolved solids). What you go for really depends on your budget, and desire to get technical and nerdy with your grow. Most have a range of 3500, which is all you will ever need for cannabis, but if you like the overkill some will read up to 9999.

1. Once you have calibrated your TDS metre, turn it on, make sure it is reading zero and put it in the water you want to test – hey presto, there’s your ppm reading. If you are using reverse osmosis water, the reading will be 0 to 10 ppm as it is completely free of minerals.

2. If you use tap water, your reading should be between 50 and 300 ppm here in the EU as standard.

3. If your town’s plumbing is old, or you are using well water from limestone strata, you may get a reading of up to 500 to 700ppm because of the mineral build up.

4. If your water is reading over 500 ppm, you need to do something about it, as it will compete with and lock out the nutrients you actually want your cannabis to uptake. Either you need to get some nutes designed to be used in hard-water areas, or you need to treat your water at home, either through carbon filters, distillation, or reverse osmosis.

Too many fertiliser salts can obstruct nutrient uptake and cause wilting. Use the DiST 4 Pocket Conductivity Tester for accurate readings.

Too many fertiliser salts can obstruct nutrient uptake and cause wilting. Use the DiST 4 Pocket Conductivity Tester for accurate readings.


This is where things get technical.

EC, or Electrical Conductivity, is a measure of the salinity of a water sample.

The theory being that saline water is charged with sodium ions and this charge can be measured by an EC metre, which tells you the conductivity of your water sample – in microsiemens per centimetre. EC works by assuming an ionic conductivity of sodium as .51 microsiemens per centimetre. This is the base charge off which metres calculate conductivity.

If your water is too saline, it can affect your plants in two ways. It can increase the toxicity of sodium at the root ball and increase osmotic pressure at the roots inhibiting nutrient uptake.

PPM measures the overall mineral content of your water, regardless of what those minerals are.

Accurate ppm readings are obtained by gently evaporating the water sample and analysing the remaining residue. Other than sodium chloride most other minerals are hardly present in nearly all naturally occurring water and are not of any real worry. These minerals are usually trace amounts of calcium carbonate, magnesium and micro traces of several other elements.

If you approach your local water authority, they can usually supply you with a mineral analysis of your local water supply.

There are conversions for microsiemens per centimetre to parts per million and back again but most metres do these conversions for you.

Organic soil and outdoor growers have an advantage again when it comes to ppm and EC. The microorganisms provide a buffer that helps protect the plant from fluctuations in ppm or EC and there is a greater margin for error when watering.

Never be complacent, though. Always check your water quality, even from rivers and creeks. You never know what could be washed in upstream during rain that could make your water toxic.


• Who thinks rain water is neutral? It is a common misconception and is actually mildly acidic. Carbon dioxide dissolves in rain and makes it into a very mild carbolic acid with a pH of about 5.6. Don’t worry, though, once it has sat for a while in a tank or dam or reservoir it releases the carbon dioxide and balances out at 7. Ever noticed how plants grow like mad after rain? That’s why.

• When you put your water through a reverse osmosis filter, it makes your water completely mineral free. Never use this water unmodified to flush your plants or as a foliage spray. RO water will strip nutrients from your plants, especially calcium and magnesium. Label your bottles clearly.

• Put aerators on your faucets. If filling a container with a hose, make the water froth and bubble to enliven and oxygenate.

• In cold climates try and keep your water at 25°C.

There you have it! Things get quite technical, so don’t worry if it takes a while to pick up. Actively working to ensure you have the best water quality you can will help minimise any potential growing problems, as well as give your cannabis what it needs to thrive. The more you know!

Part. 1: pH Good quality water is a foundation of a great cannabis grow.

Part. 3: Choosing A Water Source Choosing a water source is a crucial decision when it comes to growing marijuana.

Water quality is an essential consideration when it comes to advanced cannabis growing. In part two of out guide, we look at PPM and EC.