RDWC PPM QUESTION NEED A QUICK RESPONSE PLEASE!

legitroller · 2025-06-17T12:08:21-0600

So my grow is going awesome, I'm under 900 ppm, less is more on nutrients, great progress, will update my other thread later once I have time. So I am about to incorporate Fox Farm Open Sesame. Now, I have measured my ppm of just water, which is 75 ppm. I started by adding 1/4 tsp to a gallon of water, which took my ppm to 205. Now I subtracted my start ppm from that and end up with 130 ppm. Now my res is 20gal, I'm already at 873ppm on regular nut, so adding this will kick my ppm through the roof. What shall I do? Or should I not use it, order some dry Koolbloom, and just use that?

My feed schedule

FloraMicro 5.7ML per gal 20gal
FloraGro 6.6ML per gal 20gal
FloraBloom 3.8ML per gal 20gal

Updated Photos

Thurston · 2025-06-17T12:28:47-0600

Sorry but I only use EC and not PPM readings. As you said in your first statement, less is more. Recommend to never exceed 1.2 EC in RDWC no matter what you add but your mileage may vary. Watch your plants for signs and adjust from there.

Delps8 · 2025-06-17T12:54:43-0600

When you add chemicals to the solution, it will increase EC. Will it be enough to push the plant into toxicity? We can't tell. The plant will tell you when it's too much, so going from 873 to ~1100 might put you into the toxicity range or it might not. VPD can be a major factor in hydro so you could still be in the sufficiency range or you could be in "luxury consumption" which is sufficiency but on the edge of toxicity.

Something to keep in mind is that the goal of nutrients is to give the plants enough chemicals to be in the sufficiency range. That's all. More than sufficiency puts the plant into toxicity.

I grow in a res the holds 28 gallons and I max out at about EC 1.6 (800/500) but I also keep VPD at 1.0 in veg and 1.2 to 1.5 in flower.

legitroller · 2025-06-17T14:19:39-0600

Thurston said:
Sorry but I only use EC and not PPM readings. As you said in your first statement, less is more. Recommend to never exceed 1.2 EC in RDWC no matter what you add but your mileage may vary. Watch your plants for signs and adjust from there.

I try to use EC but my hanna hi show 1234 for EC so I use PPM

legitroller · 2025-06-17T14:41:57-0600

Delps8 said:
When you add chemicals to the solution, it will increase EC. Will it be enough to push the plant into toxicity? We can't tell. The plant will tell you when it's too much, so going from 873 to ~1100 might put you into the toxicity range or it might not. VPD can be a major factor in hydro so you could still be in the sufficiency range or you could be in "luxury consumption" which is sufficiency but on the edge of toxicity.

Something to keep in mind is that the goal of nutrients is to give the plants enough chemicals to be in the sufficiency range. That's all. More than sufficiency puts the plant into toxicity.

I grow in a res the holds 28 gallons and I max out at about EC 1.6 (800/500) but I also keep VPD at 1.0 in veg and 1.2 to 1.5 in flower.

View attachment 5469730

I have a hanna hi 98129 pen, which reads PH, PPM, EC Us it always reads in Us 1432 but claims it reads EC so I'm stuck with ppm

Delps8 · 2025-06-17T21:04:42-0600

That Hanna pen is a combo meter that reads EC, pH, and temperature. If you want it to display the EC, you should be able to switch the display.

Per that page "Selectable EC to TDS (ppm) conversion factor". I don't know what using the 0.45 would do but if you can switch to EC, that will remove all doubt.

PPM is calculated from the EC reading and PPM can be expressed as being the equivalent of NaCl (the 500 scale), KCl (the 700 scale), and another type of salt which I don't recall.

EC is the standard because there's no confusion. I use PPM for record keeping and, if I publish it, I'll write EC 1. as "800/500".

Back to your original posting—if you add chemicals to your nutrient solution, that will tend to increase the EC. Some chemicals conduct electricity better than others so. N, P, and K don't change EC all that much whereas Ca does. That's why companies that make pH meters will suggest that you add a little CalMag to RO water if you want to test the pH of the RO water. A few drops goes a long way.

In your situation, adding the extra chemicals will get you to ~1100 which is a bit high but only your plants will know if that's too much.

Oh, your plants will do better with more light.

There are signs that it hasn't been given all that much light—slender stems, a small number of larger leaves, and significant internodal space. By this stage of their growth, a cannabis plant has matured its ability to process light so the plant can take advantage of 800-1000µmol of light.

The photo below is from my most recent grow, day 44. They've been grown under a veg light so they're short and compact but there's a lot of foliage. Soon after this photo was taken, I swapped in the flower light and they ended up being about 4' tall.

Well, the plant on the left was. When I try to grow two plants, I usually end up with one tall, one short. No idea why. :-(

This is the light data for the two plants on day 44

legitroller · 2025-06-18T06:57:37-0600

Delps8 said:
That Hanna pen is a combo meter that reads EC, pH, and temperature. If you want it to display the EC, you should be able to switch the display.

Per that page "Selectable EC to TDS (ppm) conversion factor". I don't know what using the 0.45 would do but if you can switch to EC, that will remove all doubt.

PPM is calculated from the EC reading and PPM can be expressed as being the equivalent of NaCl (the 500 scale), KCl (the 700 scale), and another type of salt which I don't recall.

EC is the standard because there's no confusion. I use PPM for record keeping and, if I publish it, I'll write EC 1. as "800/500".

Back to your original posting—if you add chemicals to your nutrient solution, that will tend to increase the EC. Some chemicals conduct electricity better than others so. N, P, and K don't change EC all that much whereas Ca does. That's why companies that make pH meters will suggest that you add a little CalMag to RO water if you want to test the pH of the RO water. A few drops goes a long way.

In your situation, adding the extra chemicals will get you to ~1100 which is a bit high but only your plants will know if that's too much.

Oh, your plants will do better with more light.

There are signs that it hasn't been given all that much light—slender stems, a small number of larger leaves, and significant internodal space. By this stage of their growth, a cannabis plant has matured its ability to process light so the plant can take advantage of 800-1000µmol of light.

The photo below is from my most recent grow, day 44. They've been grown under a veg light so they're short and compact but there's a lot of foliage. Soon after this photo was taken, I swapped in the flower light and they ended up being about 4' tall.

Well, the plant on the left was. When I try to grow two plants, I usually end up with one tall, one short. No idea why.

This is the light data for the two plants on day 44

View attachment 5469774

View attachment 5469773

View attachment 5469775

Thanks for this I appreciate it So these plants have been in veg for awhile because I had problems in the beginning. When I first started, they were doing great but stopped rooting because I didn't top feed, so the roots would look for a water source. It put them behind, not to mention I killed one then had to replant and ran into the same problem . Notably, I learned if I filled the water enough to go over the net pots where the roots could actually touch the water, I would have been better off in the beginning . The learning curve of RDWC. For water, I'm using a boogie filter from my tap to filter out the chlorine. On a good note, I've been through the flooding water leaks exedra. My feed schedule has seemed to work, which I'm proud of, and has come a long way. I used to grow in soil, but I wanted to try something new, and I can say I'll never go back, and mastering EC and PPM's is awesome with a good headache. I've also learned that what works for others might not work for me cause everyone has their own experiences so you gotta filter and take things with a grain of salt and try things without the suggestions and opinions from others although we ask for help or some wanting that silver spoon instead of doing their own leg work. Then a guy of yourself comes through with a knowledgeable write-up showing that there's good help and great information I might have missed or need to take a further look into without giving all the facts and that my friend I appreciate so thank you

legitroller · 2025-06-18T07:07:25-0600

Delps8 said:
That Hanna pen is a combo meter that reads EC, pH, and temperature. If you want it to display the EC, you should be able to switch the display.

Per that page "Selectable EC to TDS (ppm) conversion factor". I don't know what using the 0.45 would do but if you can switch to EC, that will remove all doubt.

PPM is calculated from the EC reading and PPM can be expressed as being the equivalent of NaCl (the 500 scale), KCl (the 700 scale), and another type of salt which I don't recall.

EC is the standard because there's no confusion. I use PPM for record keeping and, if I publish it, I'll write EC 1. as "800/500".

Back to your original posting—if you add chemicals to your nutrient solution, that will tend to increase the EC. Some chemicals conduct electricity better than others so. N, P, and K don't change EC all that much whereas Ca does. That's why companies that make pH meters will suggest that you add a little CalMag to RO water if you want to test the pH of the RO water. A few drops goes a long way.

In your situation, adding the extra chemicals will get you to ~1100 which is a bit high but only your plants will know if that's too much.

Oh, your plants will do better with more light.

There are signs that it hasn't been given all that much light—slender stems, a small number of larger leaves, and significant internodal space. By this stage of their growth, a cannabis plant has matured its ability to process light so the plant can take advantage of 800-1000µmol of light.

The photo below is from my most recent grow, day 44. They've been grown under a veg light so they're short and compact but there's a lot of foliage. Soon after this photo was taken, I swapped in the flower light and they ended up being about 4' tall.

Well, the plant on the left was. When I try to grow two plants, I usually end up with one tall, one short. No idea why.

This is the light data for the two plants on day 44

View attachment 5469774

View attachment 5469773

View attachment 5469775

Here's a picture from today after I put up the net and tied down branches so the ones sitting lower could come up. As for the light I have a different hood I've never used a tube hood before and before you say it I like LED but there's nothing like the old school it's just hard to find a good MH in this time of 2025 vs the early 2000s when I started

legitroller · 2025-06-18T07:24:58-0600

Delps8 said:
That Hanna pen is a combo meter that reads EC, pH, and temperature. If you want it to display the EC, you should be able to switch the display.

Per that page, "Selectable EC to TDS (ppm) conversion factor". I don't know what using the 0.45 would do, but if you can switch to EC, that will remove all doubt.

PPM is calculated from the EC reading and PPM can be expressed as being the equivalent of NaCl (the 500 scale), KCl (the 700 scale), and another type of salt which I don't recall.

EC is the standard because there's no confusion. I use PPM for record keeping and, if I publish it, I'll write EC 1. as "800/500".

Back to your original posting—adding chemicals to your nutrient solution will tend to increase the EC. Some chemicals conduct electricity better than others so. N, P, and K don't change EC all that much whereas Ca does. That's why companies that make pH meters will suggest that you add a little CalMag to RO water if you want to test the pH of the RO water. A few drops goes a long way.

In your situation, adding the extra chemicals will get you to ~1100 which is a bit high but only your plants will know if that's too much.

Oh, your plants will do better with more light.

There are signs that it hasn't been given all that much light—slender stems, a small number of larger leaves, and significant internodal space. By this stage of their growth, a cannabis plant has matured its ability to process light so the plant can take advantage of 800-1000µmol of light.

The photo below is from my most recent grow, day 44. They've been grown under a veg light so they're short and compact but there's a lot of foliage. Soon after this photo was taken, I swapped in the flower light and they ended up being about 4' tall.

Well, the plant on the left was. When I try to grow two plants, I usually end up with one tall, one short. No idea why.

This is the light data for the two plants on day 44

View attachment 5469774

View attachment 5469773

View attachment 5469775

I also found this and set it to 0.45. Now, what should I set the bata to, since it's currently set to 1.9

To change the EC/TDS conversion factor (CONV)
and the temperature compensation coefficient β
(BETA)
• From measurement mode, press and hold the
MODE button until TEMP and the current temperature unit are displayed on the lower LCD. Eg. TEMP
°C.
• Press the MODE button again to show the current
conversion factor. Eg. 0.50 CONV.
• Press the SET/HOLD button to change the conversion factor.
• Press the MODE button to show the current temperature compensation coefficient β. Eg. 2.1 BETA.
• Press the SET/HOLD button to change the temperature compensation coefficient β.
• Press the MODE button to return to normal measuring mode.
Calibration procedure
• From measurement mode, press and hold the
MODE button until CAL is displayed on the lower
LCD.
• Release the button and immerse the probe in the
proper calibration solution: HI7031 (1413 µS/cm) for
HI98129 and HI7030 (12.88 mS/cm) for HI98130.
• Once the calibration has been automatically performed, the LCD will display OK for 1 second and the
meter will return to normal measurement mode.
• Since there is a known relathionship between EC
and TDS readings, it is not necessary to calibrate the
meter in TDS
The CAL symbol on the LCD means that the meter is
calibrated

legitroller · 2025-06-18T08:16:19-0600

So I did some research on how to convert my PPMs to EC

pretty much for anyone that needs to know, here's the cheat sheet.

Just multiply the PPM by 2, then divide by 1000..................... 500ppm * 2 / 1000= = .1EC. Example: my PPMs are 972*2/1000= 1.9EC

legitroller · 2025-06-18T09:06:02-0600

@Delps8 @Thurston So i did a test run...... i filled up my mixing can with 20gal mixed ll nutrent together and here are my results as followed:

Starting PPMs just water 83
With nutrient 1056PPMs
subtract 83 from that, and I end up with 972PPMs
1056=2.1EC
972=1.9EC
Here is the custom chart I made, and go by:

I ONLY USE THE TRIO, NONE OF THE OTHER.......

Thurston · 2025-06-18T09:54:29-0600

I have not used that nutrient line but in my experience those EC numbers are too high. Your plants may tolerate it for a bit, especially in veg, but eventually they will show signs of nutrient burn if not reduced.

Most of the charts provided by nutrient companies are not specifically for cannabis and thus you need to adjust accordingly.

Advisable to watch the plants closely in order to timely react to issues.

Also I have found that PK boosters do increase bud weight but nutrient solution should still not exceed max EC.
For an example, last crop used MegaCrop 1P in coco and they recommend EC of 1.4 to 1.67 during flower. I ran at 1-1.2 EC and still had tip burn. Next crop I’ll drop that down to 0.6-0.8 EC.

Delps8 · 2025-06-18T11:22:09-0600

legitroller said:
Thanks for this I appreciate it So these plants have been in veg for awhile because I had problems in the beginning. When I first started, they were doing great but stopped rooting because I didn't top feed, so the roots would look for a water source. It put them behind, not to mention I killed one then had to replant and ran into the same problem . Notably, I learned if I filled the water enough to go over the net pots where the roots could actually touch the water, I would have been better off in the beginning . The learning curve of RDWC. For water, I'm using a boogie filter from my tap to filter out the chlorine. On a good note, I've been through the flooding water leaks exedra. My feed schedule has seemed to work, which I'm proud of, and has come a long way. I used to grow in soil, but I wanted to try something new, and I can say I'll never go back, and mastering EC and PPM's is awesome with a good headache. I've also learned that what works for others might not work for me cause everyone has their own experiences so you gotta filter and take things with a grain of salt and try things without the suggestions and opinions from others although we ask for help or some wanting that silver spoon instead of doing their own leg work. Then a guy of yourself comes through with a knowledgeable write-up showing that there's good help and great information I might have missed or need to take a further look into without giving all the facts and that my friend I appreciate so thank you

Sorry to hear that you had nutrient issue but you did a good job of getting past it. The plants look healthy now. They just need more leaves. :-)

Delps8 · 2025-06-18T11:40:04-0600

legitroller said:
I also found this and set it to 0.45. Now, what should I set the bata to, since it's currently set to 1.9

It looks like the conversion factor is used to convert EC to PPM. If you want to see PPM calculated to the 500 scale, try setting it to .5. EC of 1.0 is 500PPM on the PPM scale which his common in the US and, I think, in Europe. IIRC, the folks in Australia use the 700 scale.

EC is the electrical conductivity of a solution. Some growers want to use the 500 scale which is the EC reading converted to the equivalent parts per million of NaCl. It's a completely contrived number. Other growers prefer to use the 700 scale which converts the EC reading to show how many parts per million of KCl, yet another completely contrived number.

The only reason I have used PPM is because it's more preciseise. I use a Bluelab monitor and it displays EC values in increments of 0.1. By using the 500 scale for PPM, the display will change in units of 10 so I can see it drop from, say, 600 to 590, 580, etc. If I'm using EC, the display will show 1.2 but won't change in until 1.1. The real world value of knowing that is exactly $0.00. I started doing that 4 years ago and continue to do it but it isn't of any real value.

The issue with you using your EC meter to display PPM is that it seems that neither of us understand how to set the conversion factor and that just does not bode well. Rather than futz around with something that will most likely have a negative outcome, I'd recommend that you switch back to EC.

Re the temperature beta—as with the conversion factor, I wouldn't touch it. EC does vary with temperature and I would assume that the factory setting was correct so changing it is more likely to result in a negative outcome, per above.

Perhaps the next best step for you would be to call Hanna tech support. They're the experts on how to use their products and they should be able to answer all of your questions. I have some understanding of the principles but not the details of how to set up the Hanna EC pen.

Delps8 · 2025-06-18T11:43:19-0600

legitroller said:
So I did some research on how to convert my PPMs to EC

pretty much for anyone that needs to know, here's the cheat sheet.

That's correct, for people who are using the 500 scale. Here's the skinny on what the different scales are all about.

Delps8 · 2025-06-18T11:45:50-0600

legitroller said:
Here's a picture from today after I put up the net and tied down branches so the ones sitting lower could come up. As for the light I have a different hood I've never used a tube hood before and before you say it I like LED but there's nothing like the old school it's just hard to find a good MH in this time of 2025 vs the early 2000s when I started

"old school" - yes indeed. I see you joined in 2012. You've been doing this a while!

Delps8 · 2025-06-18T12:06:54-0600

legitroller said:
@Delps8 @Thurston So i did a test run...... i filled up my mixing can with 20gal mixed ll nutrent together and here are my results as followed:

Starting PPMs just water 83
With nutrient 1056PPMs
subtract 83 from that, and I end up with 972PPMs
1056=2.1EC
972=1.9EC
Here is the custom chart I made, and go by:

I ONLY USE THE TRIO, NONE OF THE OTHER.......

As @Thurston has pointed out, that EC is a little high for hydro. The good thing about hydro is that we can adjust nutrient strength very quickly simply by adding RO.

Another factor is that VPD plays a much larger role in hydro than when growing in soil. If your VPD was high, that means that the plants would be taking up a lot more water than normal and that would mean that a lot more nutrients would be coming in. OTOH, if your VPD is a bit low, an EC of 2.1 could be a good EC.

If you end up with a little bit of tip burn, that's no big deal. Drop your EC a bit or lower VPD (lower the temperature slightly and/or increase RH slightly).

Re. VPD - if you're not familiar with VPD, this link has some good info. VPD is a handy way to use one number to represent a range of temperature and RH values. It's similar to "feels like temperature" for humans.

Re. using just three parts—that'll do the trick.

Thurston · 2025-06-18T12:43:06-0600

I agree with @Delps8 on VPD. However, not all indoor environments are stable enough when it comes to controlling VPD. Also any new nutrient line is like a new recipe, you have to cook (grow) it at least once to know the important details. From my past mistakes, I now try to be conservative with nutrients strengths and watching plants closely is key.

RDWC PPM QUESTION NEED A QUICK RESPONSE PLEASE!

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