Falling pH in hydro

Okay so what I’ve got growing on right now is a OG strain. My concern is the pH keeps falling overnight our of range. Scratched my head re did bucket, same thing. I just harvested two other plants. What the heck is causing the drop? I’m using GH plus their armor si and Cal mag plus hydroguard. Hey @peachfuzz @TDubWilly @Covertgrower - other hydro peeps. :thinking:
PS she is drinking but not enough to affect the pH ie maybe a half gallon a day… More when I seeing pH back :roll_eyes: WTF?! Help! Thanks in advance.


Small rez size in late flower will cause PH fluctuations. As root mass dies off it acidifies the liquid.


How big is your res? How hard is your water?
What are your temps?
How much air do you have being pumped into the res?
She’s probably drinking more when the ph is inline.

I think Myfriendis410 probably has the best answer already though.


But it’s early flowering and I’m using Hydroguard. Not losing enough water/solution to seeing this hard swing on previous grows that why I’m stumped.
Ro water 25ppm

Half a gallon a day in a five gallon bucket is more than enough to throw off pH.

Half a gallon a day in a 14 gallon reservoir isn’t very much.

How much do your ppms swing along with your pH. Are they staying pretty close to the same every time you check or are they changing drastically also?


I copied and pasted this from this site: https://www.maximumyield.com/perfecting-ph/2/1212

The third and fourth paragraph down tells exactly what causes pH fluctuations. The root system releasing h+ ions during osmosis to balance what it is up taking so the larger the reservoir, the more ion exchange has to take place to alter pH leading to it taking a longer time for pH to fluctuate. The reverse is true for smaller reservoirs.

What Causes pH Fluctuations in a Garden?

In a healthy, well-run hydroponic system, pH fluctuations are normal and in some instances, such as recirculating nutrient film technique with a large crop of mature plants and small nutrient volume, pH changes can be quite rapid and require frequent adjustments to stay within a narrow range for optimal nutrient uptake.

As plants remove nutrient ions from the solution, the solution’s pH drifts up or down. If left uncontrolled, the pH will often drift downwards for several days after planting a new crop, after which the pH will steadily increase.

This is due to the differential uptake of ions from the solution, with the release of hydrogen (H+) or hydroxyl (OH-) ions from the root system.

As positive ions such as cations Ca2+, K+, Mg2+ are removed from the solution, hydrogen ions (H+) are released from the root system to equalize the ratio of anions to cations in the root zone and this lowers the pH of the solution.

When the crop begins an active growth phase, anions such as NO3 are taken up, which increases the pH through the release of hydroxyl ions (OH-) into solution.

Once plants are well established, most hydroponic systems tend to see a gradual and continual increase in pH over time, which is countered with doses of diluted acid.


Ph going down a lot I usually change out systems water . If its fluctuating up I just ph down as needed.

Most times when ph fluctuates down it is caused by bad stuff in nutrient solution. When changing it out be sure to wipe down tubs with clean rags. Do not clean with soap. Just wipe down.


Thanks bro you and @peachfuzz are a great help and wealth of knowledge. The ppm’s aren’t dropping too fast she drank a gallon of water overnight since I posted. Previously I switched whole solution in bucket twice, same issues. So today I’ve added ro water with si, Cal mag in right pH now. I’ll keep and eye on it throughout the day. Thanks all.


Looking at 5.81 down from 5.88 pH. The ppm’s went up 20ppm but now in low 1000’s. So far so good :grin:

She’s tall, stretched as the Chem OG in tent at the time OG is starting to pre flower already. Here she is tonight Ms OG​:smiling_face_with_three_hearts::joy:

1 Like

Next to her is the remains of the mighty Chem OG. Which Iead to a yeild just over 3/4lbs. From an auto! Genetics and hydro can grow monsters. I’m ecstatic about the yeild and since my wife would help I sent three days cutting her down. This way I also get slightly different state of trichomes to enjoy, some harder hitter for couch lock, bedtime. So @peachfuzz whatcha think. @Dbpooper thinks I should do a photo seed. I’ve got Mango fem and a Canuk blueberry fem. Or do another monster chem OG. I like to mix it up and photos should yeild more. Thoughts @peachfuzz @Covertgrower @Myfriendis410 @Amazon66


I only run photos…
So that would be my choice… :+1::grin:

1 Like

Curious how the Canuk BB grows. I have a blueberry from a different breeder I haven’t dropped yet.

1 Like

For yield and vigor, nothing beats a female plant. Something that you may want to try.


How long would I veg, @ 24hrs light? Then flip to 12/12? Then flower for six to eight weeks? I’ve done autos only but have some fem regular seeds. If grow time is similar I’m down. Tell me more brother.

1 Like

I only use 14 hours of light for vegging using the candle stick method…
I would never have a plant on a 24 hour light cycle …
They actually use up the energy during the dark cycle that they have created during the light cycle …
18/6 or 16/8 or candle stick method…
For best results… :wink::+1:
4 to 10 weeks depending on growth rates and plant health…


Veg four to ten weeks. Then flower another 6 weeks?

I flower for 10 to 16 weeks depending on strain… :grin::+1:

1 Like