Help with Inflow & Outflow - PPM and PH

Need help with my PH & PPM in my water tank. I mix my nutrients (Jacks 321, Silica & Epsom Salt) with a target PH of 5.8 and PPM of 1,000. Been in the tank about 24 hours.

Just checked my tank and runoff. Do these numbers sound ok. I thought the outflow PPM was usually higher than inflow?

Inflow (tank) - PH 6.2, PPM 1201
Outflow (runoff) PH 6.7, PPM 910

My GG4 is 28 days old. Just started my first attempt at LST. My plant is short and squatty.


  • Seed - GG4 Autoflower
  • Sprouted - 2/9/23
  • Medium - Coco + Perlite (Mother Earth)
  • Container - #5 Airpod
  • Fertilizer - Jack 321 + silica & epsom salt
  • PH - Target 5.8 - 6.0
  • PPM Inflow - Target 900 - 1,000
  • Water/Fertilizer - 3 Times Daily (till runoff)
  • Lighting - 750 PPFD at 24”
  • Temp / Humidity - US Deep South. Temp and humidity usually high. All over the place in spring


  • Tent - 2x4 AC Infinity
  • Exhaust Fan - AC Infinity Cloudline Pro T6
  • Exhaust Filter - To be purchased
  • Oscillating Fans - 2 AC Infinity (always on)
  • Light - HLG 350R (18/6 schedule)
  • Dehumidifier - Cycles on at 65% humidity
  • C02 - No supplemental C02
  • Watering System - Halo top feed
  • Frequency - 3/day runoff of 10% - 20%
  • Outflow - To waste container
  • Water Tank/Container - 15 gallon
  • Wave Maker - SunSun Mini
  • Pump - Lifts water to top & drops back in
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It typically is. Could be anything. Maybe the solids got stuck in the soil? :rofl:

I wouldnt worry too much unless she shows signs of wear and tear. I know my runoff is always heavier when you start pouring compared to after a gallon has run thru the soil



Thanks for the reply

Do you think watering longer to produce more runoff would help?

I’m watering 3 times a day. Kinda doubt going to 4 watering would help but I don’t know?

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there’s no reason to drop it. It’s in a good range and your input is higher.

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Wow! Seriously?! What medium are you growing in? Edit: Coco and Airpots makes more sense lol

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Your pH is high for this, is your meter calibrated? The plant should be showing symptoms.

Should aim for around 5.8 in veg up to 6.3 in flower.

I would try to reduce your feed in to around 900-1000

Edit again
You don’t have to water to run off each time to desired run off as long as you get the desired run off by the last cycle. It won’t hurt to do that, but you could save some nutrients.

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@Low @PurpNGold74

Thanks for the replies.

1,000 PPM and 5.8 PH is exactly what I target and is what my reading were when it went into the tank.

The tank readings today are higher as I mentioned. I no longer use an airstone in my tank because some on here said it causes the readings to rise over time.

I have a pump in the tank that pumps water to the top of the tank and drops back in to help circulate the water. Also have a wave maker in the bottom.

Not sure why the readings go up in the tank. I guess I should readjust the tank water again by adding more water to bring down the PPM and then re PH??

Also, I included a picture and think the plant looks ok except I would have thought it would be a little deeper green? **Does the picture look ok to you?

I’ll also see about calibrating my PH and PPM pens tomorrow


pH will drift daily and has to be corrected daily until it stops, if it does. I stopped with air stones and wave makers because you introduce oxygen when you mix adjusting pH. Unnecessary. If it makes you feel better you can leave in the wave make just adjust daily if you have to.

I use general hydroponics up and down. It seems to hold pH for a longer duration than others.

If your goal is 5.8- you can pH to 5.5-5.6 and it will buy you a couple days. If it hits passed 6 I’d pH down again. Im flower 6.0 and let it drift a couple days if you need to. I like to keep flower 6.0-6.3. I use a mud mixer with a paint mixer bit in a 30 gallon reservoir.

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If you add water it will change your PPMs then you have a guessing game with nutrients. Often times tap is higher than nutrient solutions, and RO will basically take on the current pH.

You got this @Doug79

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I never check runoff numbers with coco-coir when hand watering and my reservoir with autopots i set at 5.8 and it drifts upwards of 6.5 sometimes and I’ve never had any issues.
Coco-coir seems to be very forgiving, at least with the constant bottom feed :man_shrugging:
I’ve no experience with these halos, they seem wasteful, alot of work and twice the nutrients :thinking: am i misunderstanding something here :sweat_smile:

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Every bag of coco I’ve ever seen said between 5.5-6.5 with some saying 6.0-6.5

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I forget who exactly but one of the mods grows in autopots with coco-coir and doesn’t even test ph, let alone adjust.
I use to adjust mine down when it hit 6.2 and after learning they didn’t ph at all, ive stopped making any adjustments.
Im still not brave enough to go in blind so I set it at 5.8 but they do with no issues :man_shrugging:

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@1HappyPappy @Bluntsmoke @PurpNGold74 @Low

Thanks for the replies.

Last year was my first grow. It was outside and I didn’t PH or PPM ….and my plant grew head high.

This year (my 2nd grow and now indoors) and I’m fretting over PH and PPM like I’m a mad scientist.

I’m inclined to mix and feed and not constantly recheck….and see what happens.

I appreciate all the feedback.


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