Adding Nutrients and Adjusting pH in Your Hydroponic Garden


When growing with hydroponics, ensuring you have the right nutrient mix is essential to both the growth and taste of your plants.

Adding nutrients and pH balancers to your hydroponic solution should be a multi-step process.  And before you begin, you should always make sure that you have a hydroponic EC (Electrical Conductivity) sensor and a pH sensor available.  These sensors are relatively inexpensive.  They’re available at your local hydroponics shop,, and soon  If you’ve purchased an iHarvest, you will be receiving an EC and pH sensor with your purchase.

EC Sensors:

EC stands for Electrical conductivity, which is exactly what it may sound like…it’s a measure of how well a material conducts electricity.  This is relevant to your hydroponic garden because hydroponic nutrients are made up primarily of mineral salts, which are a great conductor of electricity.   By measuring EC in your hydroponic solution, you are basically measuring the amount of nutrients that are contained in your hydroponic solution. 

There are limitations to what EC sensors can measure.  For instance, you can’t measure the amount of individual nutrients that exist in your hydroponic solution with these sensors.  You won’t be able to tell the specific amount of Nitrogen (N), Phosphorus (P), Potassium (K) or other nutrients that exist in your solution.  Sensors that are capable of this cost many hundreds, or even thousands of dollars.  So, unless you’re a professional grower you will probably want to avoid that expense.  Not to worry, though.  Measuring exact amounts of nutrients is not required for the vast majority of us, and here’s why…

N-P-K Ratio (You Can Skip This Section if You'd Like):

On each and every hydroponic nutrient solution you purchase, you will see 3 numbers.  These 3 numbers represent you N-P-K (Nitrogen-Phosphorus-Potassium) Ratio.  While your hydroponic fruits and vegetables require more than these 3 elements, these 3 elements (N-P-K) are the most important elements in your nutrient solution.  For the purpose of growing healthy and great tasting vegetables, these are the elements we will focus on in this article.

So why don’t you need to buy an expensive nutrient tester that tells you exactly how much Nitrogen, Phosphorus and Potassium (N-P-K) you need?  It’s because the N-P-K ratio is listed on your hydroponic nutrient solution, and because your fruits and vegetables will generally absorb these in equal amounts. More advanced growers may want to have a nutrient solution with more Phosphorus for flowering and fruiting plants, but we’ll save that discussion for another day.  Think of our Green Machine nutrient solution ratio this way…in every scoop of nutrients that you put into your hydroponic reservoir, there will be 10 Nitrogen’s, 5 Phosphorus’ and 14 Potassium’s.  And for every 10 Nitrogen’s, the average plant will absorb approximately 5 Phosphorus’ and 14 Potassium’s.  That means the N-P-K ratio in your nutrient solution stays at 10-5-14, and you don’t need to measure the exact amount of Nitrogen, Phosphorus and Potassium.  You can add a solution with additional Phosphorus if you’re growing more fruiting and flowering plants.

Adjusting Your EC:

Measuring your EC will produce a reading that tells you how many nutrients are in your reservoir.  More nutrients means that there will be a higher EC reading.  For simplicity, I suggest you break plants up into two categories:

Category 1: Leafy Greens and Herbs – These plants tend to desire lower amounts of nutrients in their hydroponic solution.  You should add nutrients until your meter shows a reading of between 0.8 - 1.5 EC.    One of the exceptions to this rule is Pac-Choi, which prefers a EC reading closer to 1.5 -2.0.  Spinach also likes higher EC ranges, but tastes quite good at lower ranges as well.  The chart below will help you find the perfect EC for what you want to grow.

Category 2: Flowering Fruits and Vegetables – Flowering fruits and vegetables like tomatoes, cucumbers and peppers prefer higher nutrient levels once they are mature enough to start flowering.  For these plants to flower and produce fruit, you should focus on creating an EC range of between 2.0 and 3.5.  This also applies to broccoli, cabbage (not lettuce) and hot peppers, which like to be at higher EC ranges. The chart below will help you find the perfect EC for what you want to grow.

Make sure that after you add nutrients to your hydroponic solution, and before you measure the TDS, you allow the nutrient solution to mix thoroughly with the water in your reservoir.  You can mix them manually, or you can let the pump do all the work by letting it run for 15 minutes after adding the nutrients.  If you do not allow the nutrients to mix properly, your EC measurement will be incorrect.

Adjusting Your pH:

pH is a scale used to specify how acidic or basic your water solution is.  pH is also an incredibly important aspect of your nutrient solution, as the pH level determines how well your plants are able to absorb nutrients. You can control this with your pH sensor and the pH up and down solutions.  These are provided with the iHarvest, or available online.  Keeping your pH between 5.8 and 6.5 will work very well for almost anything you want to grow.  If your pH is below 5.8, add a small amount of pH up and test again.  If your pH is above 6.5, add a small amount of pH down and test again.

Make sure that after you add your pH up or down solution, and before you measure the pH, you allow the nutrient solution to mix thoroughly.  You can mix the solution manually, or you can let the pump do all the work by letting it run for 15 minutes after adding the pH adjuster.  If you do not allow the nutrients to mix properly, your pH measurement will be incorrect.

EC and pH Balance:

Now that you’ve adjusted your EC and your pH, it’s time to check your EC again.  That’s because adjusting the pH can impact your EC reading, and adjusting your EC can impact your pH.  Make sure that both measurements are where you want them before you are done.

Maintaining your EC and pH Balance:

EC and pH balances can swing back and forth over time.  While you’re beginning to learn hydroponics, I suggest that you check the EC and TDS balance daily.  Over time, this won’t be necessary.  You’ll get a feeling for how often you need to check based on a variety of factors.  Many users find that once a system has been running consistently for a while, it tends to stabilize and you will only have to check it once or twice a week.

Nutrient and pH Chart for Hydroponic Gardens

Plant pH EC (mS/cm) PPM
(Preferred over PPM)
Arugula 5.5-6.8 0.8-1.4 560-980
Basil 5.5-6.5 1.0-1.6 700-1120
Bean 6.0-6.5 1.8-2.4 1400-1680
Bok Choy 6.5-7 1.5-2.0 1050-1400
Broccoli 6.0-6.5 2.8-3.5 1960-2450
Brussel Sprouts 6.5-7.5 2.5-3.0 1750-2100
Bunching Onion 5.5-6.8 1.8-2.4 1260-1680
Cabbage 6.5-7.0 2.5-3.0 1750-2100
Cauliflower 6.0-7.0 0.5-2.0 1050-1400
Celery 6.3-6.7 1.8-2.4 1260-1680
Chamomile 5.5-6.5 0.8-1.4 560-980
Chives 6.0-6.5 1.8-2.4 1260-1680
Cilantro 6.5 - 6.7 1.3-1.8 910-1260
Collard Greens 5.5-6.8 1.6-2.5 1120-1750
Cucumber 5.8-6.0 1.8-3.0 1190-1750
Daisy 5.5-6.5 1.2-1.8 840-1610
Dandelion 5.8-6.5 1.0-1.8 700-1260
Dill 5.5-6.4 1.0-1.6 700-1120
Eggplant 5.5-6.5 2.5-3.5 1750-2450
Kale 5.5-6.8 1.6-2.5 1120-1750
Lavender 6.4-6.8 1.0-1.4 700-980
Lemon Balm 5.5-6.5 1.0-1.6 700-1120
Lettuce 5.5-6.5 0.8-1.2 560-840
Marigold 5.8-6.5 1.0-3.6 700-2520
Marjoram 6.0-7.0 1.6-2.3 1120-1610
Melon 5.5-6.0 2.0-2.5 1400-1750
Mint 5.5-6.0 2.0-2.4 1400-1680
Mustard Greens 5.5-6.8 1.2-2.4 840-1680
Nasturtium 6.0-7.0 0.8-1.6 560-1120
Oregano 6.0-6.8 1.8-2.3 1260-1610
Parsley 5.5-6.0 0.8-1.8 560-1260
Pea 6.0-7.0 0.8-1.8 580-1260
Peppers (Bell) 6.0-6.5 2.0-2.5 1400-1750
Peppers (Hot) 6.0-6.5 2.0-3.5 1400-2450
Pumpkin 5.5-7.5 1.8-2.4 1260-1680
Radish 6.0-7.0 1.6-2.3 1120-1610
Rosemary 5.5-6.0 1.0-1.6 700-1120
Sage 5.5-6.5 1.0-1.6 700-1120
Savory 6.5-7.0 1.8-2.4 1260-1680
Spinach 5.5-6.6 1.8-2.3 1260-1610
Squash 5.0-6.0 1.8-2.4 1260-1680
Sunflower 5.5-6.5 1.2-1.8 840-1260
Stevia 6.0-6.5 0.8-1.6 560-1120
Strawberries 5.0-5.5 1.0-1.4 500-700
Sunflower 5.5-6.8 1.2-1.8 840-1610
Swiss Chard 6.0-6.5 1.8-2.3 1260-1610
Thyme 5.5-7.0 0.8-1.6 560-1120
Tomato 5.5-6.5 2.0-5.0 1400-3500
Viola 5.5-6.2 1.3-1.8 910-1260
Watercress 6.5-7.0 0.4-1.8 280-1260
Watermelon 5.8 1.5-2.4 1050-1680
Wheatgrass 6.0-7.0 0.8-1.2 580-840
Zucchini 5.0-6.0 1.8-2.4 1260-1680


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