Need help understanding PPM meter

Hydroponic DWC for beginner! What is the difference in the two PPM reading on the meter?

One has Salt at the top of meter with PPM under the reading.

The other is just PPM.

Which PPM should I be using for the nutrients?

What does the uS/cm mean?

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Both are a measure of EC or Electrical Conductivity, just a different scale, PPM parts per million that are not water molecules.


Thanks for the info!


I am interested in getting into EC readers and have been doing research on them and EC with PPm in one. I have a PPM reader already, but since getting a bubbler I don’t use it much. Do you fi d the E C reader worth the investment?

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I have bought a few different meters and PPM vs doesn’t EC matter that much as long as you use the right scale. I use EC for the simple reason that ppm pens calculate EC then apply an algorithm to approximate PPM. This is way you may have multiple PPM scales but all EC is measured in Siemens. The most important part of buying a new meter is getting a decent quality meter that you can calibrate. PH, EC, or combo the 20$ cheapo ones often aren’t very accurate. I recommend Apera units I’ve have a few and they are very good. some others on the forum also recommend blu lab

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I have all of them plus couple of different of each. I have just focused on PPM and PH. Growing in both soil andDeep Water DWC. Just trying to refine it for maximum yield and potency.

The strains are:
Black Russian
Gold Leaf
Girl Scout
White Widow
On this Grow

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I love your wooden scrog frame. I’m kinda paranoid about using PVC in my grow.

This is the one you want: NaCl scale or 500 scale which is U.S. measure.

This is the scale measure in micro siemens per centimeter.


@Myfriendis410 Thank you!! You are always the one that has come thru with a clear answer for questions I have asked…


Have I been misinformed on EC vs. PPM all this time? I hate having bad info and even more so passing it on to others.


Not sure what you Mean? This is my 4th grow and I added CO2 on my third grow. Room is sealed. My third grow was going great until the 7th week. Huge buds everywhere! And then it hit. I nuked the plants with nutrient burn…:disappointed: still salvaged a few of the plants. The taste and high were thru the roof. Invested in trying deep water DWC, which this is my first time doing and the result are crazy. Have 12 plants setup 6 in soil and 6 in DWC. Flowering was spaced out every 4 weeks. 4 plants in then wait add 4 more plants to flowering! First set has 3 weeks to finish. That is the reason for my question so that I don’t make the same mistake again. Buds are hard as a rock and sticky beyond believe! I took my time and research rare strains! I have Black African Magic and Purple African Magic in veg stage!


EC is in micro siemens as well. The conversion is: EC of 1.0 = 500 ppm NaCl scale and 700 on KCl scale. So an EC of 2.0 would be 1,000 ppm 500/NaCl scale. It’s just another means of measuring solids in liquid.

A good rule of thumb with hydro or media (coco) grows is to keep liquid at or below 900 ppm and 1,100 to 1,200 in flower. You should not have any issues with those numbers, unless running insufficient lighting.


Would it be the same when you add CO2 or should the nutrients be higher or lower? I used clay pebbles. The root mass filled the 5 gallon bucket. They are mainly off white color unless I change the Nutrients they are darker for a day or so.

This is my main light

AC Infinity IONFRAME EVO6, Samsung LM301H EVO Bar LED Grow Light 4x4, 1074 Diodes

I also have two 400 watt mars light. Then couple off brand I started with

So we see a lot of posts with CO2 and have some observations:

Optimizing your grow and grow space should always be number one. Adding CO2 to a crappy setup will just give crappy results.

CO2 exhale bags are generally worthless. They do not produce a meaningful amount.

Conditions have to be set up to utilize CO2: very high PPF (light), sealed environment, elaborate heat rejection has to be used.

Very high nutrient load under CO2.


I tried these as well… Borrowed a CO2 meter…
They add very little… Just as @Myfriendis410 said.

I’d save your money… Put it towards other good equipment. Like lights… If there’s one thing I could recommend to new growers it’s:

Do homework, make a plan, save get good equipment rather than doing it quickly and getting equipment you’ll end up replacing.

Once you’ve got all equipment and setup correctly everything gets much easier.

It’s worth it.


The room is completely sealed no leaks! CO2 level is at 1,200 PPM during light hours.

With that said how high should the nutrient go up? And should the PPM on the CO2 increase as well?


The buds are really packing it on with the CO2. Just need expert advice with small tips to push it over the edge.


@Letsgetit60 Sorry… I don’t know how I missed that you said you had a sealed room… Mine was a tent.

I apologize… Old eyes.

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