Hydro resevoir ph fluctuates

Im running a 40 gallon reservoir on a drain to waste coco setup. So far so good except my ph after setting it 5.9 with ph down always raises back to my waters natural ph of 6.3

This doesnt seem to cause any issues as the plants are flourishing. My question is how does one make the ph stabilize. Im using the GH series, hydrogaurd and Silica.


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The only way to maintain PH in a rez is to run a controller to dispense automatically. This is completely normal and one of the things you have to do. You can PH down to 5.3 and let it range back up which is what I do.

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5.3 is a little low eh? I had been doing it to 5.8 but next day its bsck to 6.3

For me, not mixing continuously helped with the ph swing. I mix once a day for 15 b4 the feed.

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If I understand it all correctly…
Henry’s law says the CO2 in the water (which is acidic) will dissipate until it’s in balance with the levels in the air. Aerating or circulating excessively really accelerates the off gassing, and is one reason for rises in res pH.

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Im using a pump 24/7 creating an aerating waterfall in the reservoir.

Now we are getting somewhere. So the excess aeration and current in the water from my pump " which is my old clone king cloner pump " is causing my issue, that about right?

I thought aerating the water by creating a waterfall was the proper way to run a reservoir with the addition of hydrogaurd. Was i wrong?

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Well, it could be some of the issue. There’s more variables involved, like how much CO2 was in the water in the first place? It’s different for everyone, so some it helps and some not so much. Water needs to be oxygenated, so you’re not doing anything wrong exactly.

There’s plenty of other reasons, like your plants could be gobbling up the acidic nutes, signaling an increase needed in ppm’s…

Just throwing out some ideas to consider.

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Hmm thanks. I’m running between 5 and 6 hundred tds feeding twice a day but switching to 3 soon.

My plants didn’t seem to like 700 tds so i dropped back to 500.

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Actually, I was thinking along the lines of a more circulatory system, like (R)DWC.
A drain to waste coco system wouldn’t need that much oxygenating. Just some occasional stirring, like @Poseidon1 had mentioned. So maybe in your case it is being over aerated?

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I meant to say i was switching to Jacks 321 soon but it came out just the number 3 on my above post! Lol!

I would have to agree then and will set my pump up on a timer as i had been letting her rip taterchip 24/7 wide open non stop. Sounded like a waterfall.

Thanks :blush:

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Low salt levels will also allow PH to fluctuate too.

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I agree, aerating will drive the ph up. Going more than .1-.2 in 24 hours or less is a lot though. I seen you were gonna use cycle timer, you may also try turning pump down or using less/smaller air stone.

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I look at yhose plants, some of the healthiest plants going. .beautiful fingered leaves.

Thank yall, never thought of co2 presence in water, H20, CO2, duh. Or yhe possible cause in rise.

Also would have never thought it would be advised or practiced to initially target 5.3. to account for the rise.

I look at 5.5 to 6.2 as sacred ground snd not venture out.

Auto pots, htdro , any type of system with resorvoir, this pH rise, possibility in all?

It’s always a thing. Pool maintenance guys struggle with it too, as well as aquarium guys, although they actually add CO2 into their tanks to counter it I guess. It’s a pretty well known phenomena in the (R)DWC circles from what I’ve read, and considered “typical” to some degree.

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I already see a difference since i put it on a timer. I think the ph fluctuating from 5.8 to a max 6.3 may actually be doing some good as my plants are exploding with new growth.

I may have to remove two as I’m getting crowded.

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Wow! Those are looking REALLY good!!!

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@Myfriendis410 have you ever used a continuous ph meter in your setup?

When making Whisky we often used a mash ph stabilizer in the distillery. A few spoonfulls held the mash at 5.8. Without it it fluctuated. So my question is do they make a ph stabilizer for hydroponics?

I think a lot of the problem is the salt content in our nutrient mix is much more dilute than your mash so it ‘resists’ PH swings poorly compared to your oatmeal lol. I haven’t seen stabilizers but there are automatic dispensing devices for maintaining correct PH.

I have come to worry less and less about my rez swinging from low to high and there is a good argument that it lets the root zone see more of the nutrients in the medium.

My last job before retiring was working in a craft distillery: 1,000 gallon cooker, 750 gallon tophat still with 7 rectifiers. Four open-topped fermenters etc. We did bourbon, corn whiskey, brandy (right next to a wine storage facility lol) and specialty spirits. Caviar lime Vodka, a James Beard Award winner gin etc. It was strenuous but fun.

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Yes i too am seeing the wisdom of letting it fluctuate. I am purchasing a continuous meter to keep up with it better. So far so good. I gotta do a major defol soon as i was unprepared for the explosive growth of continuous feed.

These Cinderella 99 crosses are some amazing genetics.

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