I’m often asked about nutrients – what brands I’m using, my feeding schedule, if I measure pH, etc.
To be honest, I like to keep my indoor gardening really simple.
I try to grow as much as I can inside my apartment without being too precious or fussy about the week-to-week maintenance.
I use local water (NYC tap is great), inexpensive nutrients (whatever I have on hand) and I just top up my indoor gardens whenever the water levels are low.
I don’t purge and re-fill my gardens with fresh solution each time, and I only do a deep clean in-between plantings.
Personally, I find it’s very doable to grow healthy, thriving plants without over complicating things!
But, even in a home hydroponic setup, it’s helpful to understand terms like pH and EC.
These measurements are key to growing healthy, productive plants.
And if your indoor gardens are showing signs of stress, understanding pH and EC will allow you to troubleshoot any issues.
It took me a bit of time to understand them (AP chemistry made my brain hurt), so I’ve mostly held off on answering in-depth nutrient questions until I got a good grasp of everything myself!
Lately, I’ve been attempting to significantly increase my harvest size, trying out larger tower systems and growing trickier plants like strawberries.
So with all the experimenting, I’ve started to measure pH and EC more regularly and picked up this pH testing kit and this EC meter.
In today’s article, I’ll explain what pH, EC and PPM mean for hydroponics and how you can manage them to get the best results with your herbs and vegetables.
plants need the proper level of nutrients to form fruit
First, let’s start with pH.
What is pH in hydroponics?
pH measures how acidic or alkaline your water and nutrient solution is, on a scale from 0 to 14.
- 0 = very acidic
- 7 = neutral
- 14 = very alkaline
In hydroponics, most herbs and vegetables prefer a pH range of 5.5 to 6.5. Staying within this range ensures your plants can absorb essential nutrients effectively.
Why does pH matter?
A pH that is too high or too low can block nutrient absorption. Even with a well-mixed nutrient solution, the wrong pH can cause deficiencies.
Think of pH like the bouncer at the club deciding which nutrients get in.
Signs of pH imbalance:
- Yellowing leaves
- Slower growth
- Nutrient deficiencies despite feeding
What is EC?
EC stands for electrical conductivity, which measures the concentration of dissolved nutrients in your solution.
- High EC: strong nutrient solution (too high = root burn)
- Low EC: weak nutrient solution (too low = slow growth)
Leafy greens like lettuce usually thrive at 1.2 to 2.0 mS/cm.
Large crops like tomatoes and peppers need more nutrients to properly form and develop fruit. They prefer an EC between 2.0 to 3.5 mS/cm.
Most nutrient brands will recommend target EC ranges on their labels.
Think of EC as the “seasoning” in your plant recipe – not enough and the dish is bland, too much and it’s overwhelming.
What about PPM?
PPM (parts per million) is another way to measure nutrient strength.
Like EC, it measures the concentration of dissolved solids (nutrients and salts) in your hydroponic solution.
In simple terms, PPM tells you how many milligrams of dissolved solids are present per liter of water.
So PPM and EC both measure nutrient strength, but they express it differently.
- EC = measures electrical conductivity (how well the solution conducts electricity)
- PPM = estimates the actual amount of dissolved solids (nutrients + salts) in the water
I recommend getting an EC meter like this one and focusing on EC. Here’s why:
How is PPM related to EC?
Most PPM meters are actually EC meters with a built-in conversion.
They take the EC reading and multiply it by a factor (either 500, 640, or 700), depending on the manufacturer.
PPM readings can vary depending on which scale your meter uses.
For example:
| Conversion Factor | EC (mS/cm) → PPM |
| 500 scale (TDS) | EC × 500 = PPM |
| 640 scale (European) | EC × 640 = PPM |
| 700 scale (Australia/Hanna) | EC × 700 = PPM |
This inconsistency is why I recommend using EC instead of PPM. EC is universal and doesn’t vary by region or brand.
If you already have a PPM meter, it likely works fine. Just be aware of its scale and stay consistent!
Otherwise, using EC directly is simpler and more reliable.
Quick Comparison: pH, EC and PPM
| pH | EC / PPM | |
| What it measures | Acidity / alkalinity | Nutrient concentration |
| Ideal range | 5.5 – 6.5 | 1.2 – 3.5 mS/cm (depends on plant) |
| Why it matters | Controls nutrient absorption | Indicates nutrient strength |
| How to test | testing strips | EC meter |
In hydroponics, EC is preferred over PPM because:
- EC is consistent across all meters worldwide
- PPM can cause confusion (different scales)
- Most nutrient brands recommend EC targets, not PPM
Read more: Understanding N-P-K for Hydroponic Gardening
plants need the proper level of nutrients to form fruit
Which is More Important?
For home hydroponic growers, pH is slightly more important to check regularly.
Even if your nutrient strength (EC) is perfect, the wrong pH means plants can’t absorb those nutrients well.
Most hydroponic nutrients for home use won’t need constant EC tweaking, because premixed nutrients are designed for balanced feeding.
But, pH can fluctuate easily due to water source, plant uptake, and even air exposure.
Think of it like this:
- pH: Critical (controls nutrient absorption)
- EC: Helpful (tells you how concentrated your nutrients are)
- PPM: Just a different way of reading EC
If this is all too confusing for you, use an all-in-one fertilizer like Aerogarden’s liquid plant food!
It’s specially formulated to be pH buffered, and should work with most water sources.
Read more: Everything You Need to Know About Aerogarden’s Nutrients
Hydroponic Nutrients for Indoor Gardens
Balancing pH and EC in hydroponics doesn’t have to be complicated.
Focus on keeping pH stable first and check EC periodically to ensure your plants are getting the nutrients they need.
With a few easy habits, you’ll enjoy healthier plants and better harvests.
Read more: Plant Nutrients 101: A Complete Guide
My advice:
If your indoor gardens are showing signs of stress,
- Check pH 2–3 times a week
- Adjust pH with pH Up or Down solutions as needed
- Check EC when mixing nutrients
If you’re looking for a simple tool to monitor nutrient strength, the Letpot EC meter is accurate, beginner-friendly, and easy to use.
I wrote a guide on how to use it here.
Every plant has it’s own pH and EC ranges. I put together a helpful chart for various vegetables here.
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