RDWC PPM QUESTION NEED A QUICK RESPONSE PLEASE!

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

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.

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.

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.

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

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

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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

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