hardcore ph fluctiontion

hello everyone i just got a new 300liter res and im having some problems. I adjust my ph to 5.8 and when i come back the next day it jumps to 7.5 sometimes a bit higher. Now i have used almost half my ph solution bottle in the past 3 days keeping my ph right. Anyone have any ideas?

i have a 300l airstone in there and nutes are advance nutriets and i also put hydrgen peroxide in.

I turned the airstone off today just to see if thats what is making the ph fluctuate.

If you are using tap water try testing the ec of the plain tap water. If it's high you have hard water and the calcium carbonate neutralizes the acid. Are you also getting a white powder?

I am on RO water. dont think so on the white powder. dont exactly know what u mean but the answer is no white powder

RickWhite said:

If you are using tap water try testing the ec of the plain tap water. If it's high you have hard water and the calcium carbonate neutralizes the acid. Are you also getting a white powder?

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bushmang said:

I am on RO water. dont think so on the white powder. dont exactly know what u mean but the answer is no white powder

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RO water should have a PH of 7 to begin with. I don't know if the acid you are using could somehow be reacting with the peroxide. Another possibility is that you are not adequatly mixing the acid and allowing it to stand for a while before testing and getting a false reading. Then again if you have certain microbials in your root zone they could be causing that problem. Are your roots white or brownish?

What is the EC/ppm of your nutes, and when you say pH solution do you mean a phosphoric acid based product??
RO water is actually tougher to stabilize than harder water because of the lack of buffering compounds.. Phosphoric acid reacts with alot of stuff to form some excellent buffering agents in the 6-7 range..
Its not the H2O2.. Any pH shifts caused by that are going to be short lived.. My guess is your nutes aren't providing adequate carbonates etc for the pH down to do its job, and they aren't in the water..
One thing that increases buffering capacity nicely is peat.. Soak some peat in your res, and the pH will fall, and tend to be more stable in that range..

Do you think i should just pump out the water clean the tank and start over?

born2killspam said:

What is the EC/ppm of your nutes, and when you say pH solution do you mean a phosphoric acid based product??
RO water is actually tougher to stabilize than harder water because of the lack of buffering compounds.. Phosphoric acid reacts with alot of stuff to form some excellent buffering agents in the 6-7 range..
Its not the H2O2.. Any pH shifts caused by that are going to be short lived.. My guess is your nutes aren't providing adequate carbonates etc for the pH down to do its job, and they aren't in the water..
One thing that increases buffering capacity nicely is peat.. Soak some peat in your res, and the pH will fall, and tend to be more stable in that range..

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No, it can only get better..

born2killspam said:

What is the EC/ppm of your nutes, and when you say pH solution do you mean a phosphoric acid based product??
RO water is actually tougher to stabilize than harder water because of the lack of buffering compounds.. Phosphoric acid reacts with alot of stuff to form some excellent buffering agents in the 6-7 range..
Its not the H2O2.. Any pH shifts caused by that are going to be short lived.. My guess is your nutes aren't providing adequate carbonates etc for the pH down to do its job, and they aren't in the water..
One thing that increases buffering capacity nicely is peat.. Soak some peat in your res, and the pH will fall, and tend to be more stable in that range..

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You are over simplifying it a bit. First, H2O2 can give of a highly reactive singe O atom and it's hard to predict what kid of issues that can cause.

Secondly, buffering prevents shifts in PH in both directions, not just upward. And you don't want to create a heavy calcium phosphate salt issue in the name of buffering. Those heavy salts can also push the nutrients out of solution causing toxic conditions.

Pure water should change PH quickly with the addition of acid. What may be happening is that he has some microbial conditions that are causing a rise in PH.

I'm guessing its not buffering it high, that it shifts at a fairly steady rate across the swing.. I guess its not a bad idea to ask how many drops of pH down it takes to drop from 7.5 to 7.0, compared to 7.0-6.5, compared to 6.5-6.0 and so on..
Microbial action tends to drop pH, and he's tossing H2O2 in there so I doubt that.. And furthermore, H2O2 effects would be short lived, especially in high pH solution..
As for buffering, it depends on the compounds doing the buffering, and the current pH as far as buffering directional capacity goes..
Hydroponic fertilizers usually contain alot of nitrate N.. Uptake of this lowers the [H+].. Hydrogen/dihydrogen phosphates are supposed to combat that..
And wtf are you talking about pH down byproducts pushing nutrients out of solution?? Study up on your solubility charts..

the ph is at 7.1 now and 50 ml of ph down in the 300 l tank barely makes it move down.

How far would 50mL have swung it earlier?? This sounds like that buffering I was talking about, but the wrong combination of buffers to stabilize it at high 5's..
What is your EC/PPM and how does that flucuate each day??

Microbials can certainly cause more alkaline conditions and a host of bacteria break that H2O2 down releasing that free O radical. I have no idea what kind of conditions that can cause when adding a plethera of other chemicals.

But there shouldn't be any buffering using RO water. A small amount of acid should cause a dramatic shift. Again, I would check the ec of the alleged RO water before adding anything.

Dude, as various salts build up the buffering capacity goes up.. What we hope is that the ratio of those salts buffers at our target pH.. Anybody who's managed a res knows that pH tends to get less erratic as time goes on, and more than a few ppl have seen the pH want to lock into some undesirable range..
I'd need to know alot more specifics to help further.. Again I don't even know the EC/ppm, or what he is using for pH down..
And as for the Advanced Nutrients, well merely saying you're using those is kind of like saying you had food, or a food-like substance for dinner last night.. They make more products than ACME
And H2O2 doesn't need any microbial help to break down when diluted to virtually nothing in a more basic environment..

born2killspam said:

Dude, as various salts build up the buffering capacity goes up.. What we hope is that the ratio of those salts buffers at our target pH.. Anybody who's managed a res knows that pH tends to get less erratic as time goes on, and more than a few ppl have seen the pH want to lock into some undesirable range..
I'd need to know alot more specifics to help further.. Again I don't even know the EC/ppm, or what he is using for pH down..
And as for the Advanced Nutrients, well merely saying you're using those is kind of like saying you had food, or a food-like substance for dinner last night.. They make more products than ACME
And H2O2 doesn't need any microbial help to break down when diluted to virtually nothing in a more basic environment..

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You are way wrong. BTW, I have 2 semesters of majors level general chemistry plus qualitative analysis and two semesters of majors level organic chemistry. I think I just might know a little bit about the subject.

Buffering would only occur if you start with a hard alkaline water and use acid to bring it down to where you want. When you do that you get salts that may not be desirable and they make it impossible to properly measure EC because the salts may contain cations that can scew the measure.

The best thing to do is start with pure water and use a small amount of acid to bring it down to acceptable range. I understand that in some biological systems buffering is an advantage (such as human blood) but I think you are making a mistake in assuming this is what you want in this situation.

Ok, well what does your university resume tell him to do when the problem repeats itself after replacing the res and wasting the nutes??
Buffering is critical in horticulture.. Soil does alot for that.. In hydro, recipes need to be tweaked to produce these buffers..
BTW the human circulatory system is a hydroponic system..

born2killspam said:

Ok, well what does your university resume tell him to do when the problem repeats itself after replacing the res and wasting the nutes??
Buffering is critical in horticulture.. Soil does alot for that.. In hydro, recipes need to be tweaked to produce these buffers..
BTW the human circulatory system is a hydroponic system..

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Dude, I think it's great that you are thinking about what you are learning and applying it to what you are doing, but you don't want to apply those concepts Willy nilly.

Building a chemically buffered solution in a hydro setup can cause other problems. Namely, you can have solubility issues. And as I mentioned, if you create a condition with a large concentrations of cations such as Mg which is commonly found in hard water you can't accurately measure the EC of the nutrients.

Now a system that has a buffering effect is another matter. This is primarily accomplished by using large reservoirs as it is harder to cause changes in 100gal of water than in 5gal obviously.

What I would suggest for the OP is to test the water. Pure water should have a PH of 7 and an EC of zero. I have dealt with hard water and had the same problem as the OP. Problem was the water was so saturated with calcium carbonate that it just keep neutralizing my acid over time and causing copious amounts of white precipitate (calcium phosphate) to be produced. I had literally pounds of the stuff.

The thing to do is start with good water.

Just curious but are your roots sitting in your reservoir?

I've had similar problems and think this might be related to severely fluctuating PH.

I'm not 100% sure on this, it's just a theory of mine after building a new system and changing a few things to make the roots not hit the res and everything perfectly stable all week long.

Dude, nutes and phosphoric acid form some great buffers.. Look into what happens when phosphoric acid is mixed with KOH or NaOH, then google/wiki those products.. Alot more are formed with random salts in the water, but it is true that sometimes the pros of those additionals don't outweigh the cons.. Peat will add alot of stability along with dropping pH.. Some ppl soak some in their water before adding it to the res..

Building a chemically buffered solution in a hydro setup can cause other problems. Namely, you can have solubility issues. And as I mentioned, if you create a condition with a large concentrations of cations such as Mg which is commonly found in hard water you can't accurately measure the EC of the nutrients.

Now a system that has a buffering effect is another matter. This is primarily accomplished by using large reservoirs as it is harder to cause changes in 100gal of water than in 5gal obviously.

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In all your effort to out do me, you've overlooked the fact that he's using 300L of 'RO' water and he's having these problems.. If he took your advice of starting fresh with new water, he'd waste $50 or so and likely repeat the problem

ok guys here are the readings of everything

ro - ph 7.9 ppm 100

tap water ph - 9.0 ppm-400

i appreciate u guys argument i learned a lot from both sides.. what do you suggest?

I was thinking about dropping the ph to 6 or something like that before i mix the nutrients and then fine tuning once the nutes are in.