PPM and a few misc questions

I just want to start by saying thanks to everyone that has given me input so far. This is a great community and I really appreciate it as a beginner.

Ive been trying to incorporate a lot of great advice that ive been given here in the last few weeks that I wish I knew from the start. Well anyway I think I’m in about week 6 of flower, plant 1 seems a week ahead of plant 2. I started recording PPM a few weeks ago trying to keep the levels around 1000. Well this week plant 1 read 1400 (Still a little high) and plant 2 read a whopping 2400. Now I know that’s fkin terrible and I’m worried I just sentenced plant 2 to death. Last week i started cutting nutes down half like i was directed to. I think the obvious step here is not more nutes for plant 2 in the coming weeks, right ? Do I need to flush the plant, is that how that works? The plant seems healthy with a little bit of burning on the tips and minor wilting so am not sure what to do. I will add a picture of my feeding schedule ive been tracking but pay no attention to the week listed on there because I got all fked up on weeks. But I think I’m on week 6 or 7 of flower now.

Plant 1


Feeding Schedule

  1. Indoor or outdoor? - size of grow? Indoor 2 plants
  2. Origin of seeds? ILGM
  3. Regular, feminized, or autoflower? Autos
  4. Origin of water. PH, EC/TDS of source water? Distilled - 7.0
  5. PH and TDS/EC of if mixed solution? 6.5 mixed with solutions
  6. Grow method? Soil
  7. Nutrients or fertilizer system used. Fox farm trio
  8. What type of lighting are you using? LED, HID (MH, CMH, HPS), or Fluorescents? Please elaborate. Spider farmer sf1000
  9. What are the temps in your growspce? Day / Night? Day - 76-81F Night - 68 - 72F
  10. What is the RH = relative humidity in your growspace? Day / Night? 40-60%
  11. AC, Humidifier, De-humidifier? Dehumidifier and two fans 6inch and 12inch osc
  12. Do you have a Ventilation system? Size? 4", 6"? Spider farmer 4inch carbon
  13. How long have you been growing? First time
  14. What budget have you set in order to grow successfully? No budget
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Flush the plant at 2400 with distilled or r/o until it’s around 1000-1200. If it’s

Stay on water only on both until run off drops to 800-1000 then feed again. Continue in this fashion.

It will take several gallons to flush it out.

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Thanks for the reply. So you just pour distilled water through the plant until the runoff reads the target area ?Is this done of the course of a few weeks ? Do you do this back to back on the same day? Do you need to fear overwatering or is that the point here to flush out the nutes ? I suppose I can watch a video on how to flush as well.


No you do it in one session. So next time you have to water flush it until you are in range. :call_me_hand:t3:

Overwatering is caused by frequency of watering, not how much you pour in at once.


2400 ppm in soil isn’t terrible and you have not killed your plant. Autos do respond better to a lower nutrient level than photos but if it were mine I’d just do water-only until the TDS drops down to 1,200 ppm or so then resume (light) feeding.

That light you have is insufficient to flower off one plant FYI. You do need more light in the grow space.


okay thank you will do

Roger. Yea I heard this back a little bit ago so I ended up getting a 2nd light.

This should be enough for each no?


The metric I use is 200 watts per plant. Good lighting results in tight plants with dense flowers. It’s the most important environmental factor for a productive grow.

You can grow weed with your setup, but you will get a higher quality product with adequate lighting.

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ah okay noted. i will look into this for future grows. thank you guys

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So to clarify if you were to grow 4 plants you would want at least 800w light ?

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Correct, or a combination of lights adding up to 800.

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I run between 200 and 240 watts per plant. My lights are homemade from gen 1 Samsung diodes so not as efficient as newer offerings from HLG and others. Even adding one more of that same light would make a difference in yield numbers. You also have higher nutrient uptake and a more healthy plant with the right conditions.

Here’s one I harvested last August under 200 watts:

That was a 12 oz. plant done in coco/3 gallon/Jack’s nutes


beautiful and great information, thank you. I have also heard good things about jacks.

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With the ever changing technology watts isn’t the best metric. Use the amount of PAR The PPF rule for optimal lighting is 65µmol (Usable PPF) per square foot

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So I remember reading about this and the rule that i found when reading was

“To optimise your grow it is recommended that your plants receive 500-1000 µmols of PAR light for every m² (PPFD)” (this is from migrolight)

I had some trouble understanding all of this. So does this mean in a 3x3 tent you would want 500-1000 umols? 3x3 tent is almost 1 meter I think right? Sorry never was good with math.

PPFD is the density of photosynthetic Photon Flux. Not the total amount. You want to have between 500 and 1000 PPFD at the canopy, but you will also need to make sure the total usable PPF is adequate to power your grow area

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PPFD (Photosynthetic Photon Flux Density) is defined as a measure of lighting density, and as the definition includes “density,” it already considers space in how PPFD is calculated. You can disregard whatever you were told about PPFD per square meter. PPFD alone is sufficient.

It is necessary to consider space if using PPF rather than PPFD, as lighting density is not considered in the calculation of PPF.

It is also valid to say watts per square meter. The general metric is 35 to 50 watts of quality lighting per square foot of canopy space to achieve the needed PPFD.

I run my plants at these levels:

Seedling: 300 PPFD
Veg: 600 PPFD
Flowering: 1,000 PPFD

There is a phone app called Photone that does a decent job of estimating PPFD with your cell phone camera.

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fantastic, thank you.

So using photon I recorded both plant from the canopy at 550 ppfd. So it seems I’m very short and these lights aren’t cutting the cheese. Right now they’re sitting about 16-18 inches from the canopy. Would moving them closer be beneficial or would that create new issues. I realize now that next grow with more than 2 or more plants will require better lights.

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