A Community and Forum For Aquaponic Gardeners
PH Fluctation
To all the Boffins out there I need serious Help!!!!
Equipment:
1x1000 lt IBC F/T
1x250 lt Clarifier
1 x250 Bio Filter
1x500 lt Sump
6 raft beds total 1800lt
1 x Pump 6000 LTH
1x Air blower total 22 Air Stones
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Water
KH 432 mg/L (4 x over the the accepted amount being 61 to 120 mg/L) or ppm75 to 150
NH3/4 0
N2 0
N3 5
Water temp at night 10 deg .Daytime 20 deg
Heres my problem
My PH being constant at 7 suddenly droped to 4.1 (I'm using 2 types of PH testers)
2 hours later went up to 5.6.
No chemicals were added what so ever to the water .
Presently I'm in a fish less cycle& my raft beds are stocked with plants.
I cannot find answers so please help.
Many thanks.
PS.for those who are having hassles with bio-filter or BIO BALLS Heres my Invention
you can use SHADE CLOTH with an airstone works like a dream .the more cloth the better.
Replies to This Discussion
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Permalink Reply by TCLynx on
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Do you have algae in the system?
It is not uncommon for the pH to suddenly drop late in the cycling process not long after the nitrite drops. It tends to happen as the bacteria really get going and manage to use up much of the buffering capacity of the water, this may mean you need to monitor and adjust how you are buffering your water accordingly.
If you have algae going on through, the time at which you measure the pH can tell you a bit. See overnight algae will use up dissolved oxygen and give off dissolved carbon dioxide which will act as an acid in the system bringing the pH down and then during the day when the algae has access to light it will be using up the dissolved carbon dioxide and therefore bringing the pH up (and if there was some buffer dissolved over night it may suddenly be too much as the acid is removed from the water during the day and the pH can go way high.)
So if algae is giving you the problem, your pH is likely to be lowest right before dawn and it will be highest in the late afternoon.
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Permalink Reply by Colin Fisher on
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Also my KH is 4x higher than what it should be .At present it is 432mg/L where it should be between 61 to 120.
TCLynx said:Do you have algae in the system?
It is not uncommon for the pH to suddenly drop late in the cycling process not long after the nitrite drops. It tends to happen as the bacteria really get going and manage to use up much of the buffering capacity of the water, this may mean you need to monitor and adjust how you are buffering your water accordingly.
If you have algae going on through, the time at which you measure the pH can tell you a bit. See overnight algae will use up dissolved oxygen and give off dissolved carbon dioxide which will act as an acid in the system bringing the pH down and then during the day when the algae has access to light it will be using up the dissolved carbon dioxide and therefore bringing the pH up (and if there was some buffer dissolved over night it may suddenly be too much as the acid is removed from the water during the day and the pH can go way high.)
So if algae is giving you the problem, your pH is likely to be lowest right before dawn and it will be highest in the late afternoon.
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Colin, where do you get this information about what the KH "should" be? I admit hard water can be a pain but I'm not sure that there is a set range that it has to be in for Aquaponics. With really hard water and an over abundance of calcium carbonate you may experience problems with the pH staying high and perhaps having too much calcium can give you issues with potassium precipitating out of solution and having potassium deficiency problems (I see this with my big system where about 40% of the media is shells) but that system has a very solid pH of like 7.6 and though the plants struggle and I have to supplement with chelated iron all the time, I still manage to grow things.
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I had my water tested at the lab cost an arm & a leg & that was their results .the water on our mushav is very hard soap dosent lather .
TCLynx said:Colin, where do you get this information about what the KH "should" be? I admit hard water can be a pain but I'm not sure that there is a set range that it has to be in for Aquaponics. With really hard water and an over abundance of calcium carbonate you may experience problems with the pH staying high and perhaps having too much calcium can give you issues with potassium precipitating out of solution and having potassium deficiency problems (I see this with my big system where about 40% of the media is shells) but that system has a very solid pH of like 7.6 and though the plants struggle and I have to supplement with chelated iron all the time, I still manage to grow things.
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Well, ya don't want to use soap in your aquaponics system anyway.
If you pH has dropped then I expect you will be able to manage with the hard water at least to an extent. I know with my well water if I'm having to top up all the time with it, my pH stays higher than I like but in my systems where I didn't use shells, the pH will come down if I'm able to use rain water to top up part of the time and I haven't had the potassium and Iron problems in those systems as I'm able to use potassium bicarbonate to keep my pH buffered sometimes.
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Permalink Reply by RupertofOZ on
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Ok... lets clear up a couple of definitions firstly...
Hardness is defined by two different values... carbonate hardness (kH) and general hardness (gH).... and is often expressed in tests as "total hardness"...
In many aquaria circles the terms "temporary" and "permanent" hardness are often used... but that's realy a misnomer..
"Hard" water.. such as seen when soap doesn't lather.... is general hardness... not carbonate hardness...
So what do the two terms... carbonate and general hardness.. relate to...
Carbonate hardness... is the measure of the buffering capacity of the water... the ability to resist acidification... usually Calcium Carbonate..
General hardness... is the measure of the positve mettalic ions in the water... usually Calcium, Magnesium and Iron...
(To confuse matters.. both are often expressed as a value of the amount of Calcium Carbonate content... but ignore that...
)It is possible, and often the case.. that water with a high general hardness... also has a medium to high carbonate hardness... but not necessarily so...
It is also possible for water with a general hardness to have a low pH... but very rarely... and almost artificailly...
It is virtually impossible however... for water with a high carbonate hardness... to have a low pH.... it's a basic contradiction, as the carbonate buffer is exactly what resists pH decline...
So while it's possible that your water lab test might have returned a high carbonate hardness value (kH)... or even (incorrectly) expressed the total hardness as a"kH" value...
The reality is you have "hard water"... general hardness (gH)... and only RO will fix that... but hard water isn't detremental, other than to your laundry, and/or scaling of your plumbing... and it's actually a benefit to plant growth...
You may also have a high level of carbonate hardness (kH) Colin... but if so then your pH tests are wrong... totally wrong...
It's almost impossible to have pH values that you are reporting... even with general hardness....
Something just isn't right with those test values... unless they're being influenced by external factors... chemical/acid addition... or, possibly an out of calibration RO unit...
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HI rupert many tks for a reply.
firstly my normal pl is 11 although the test done they came out with a ph of 7 which I find hard to believe.
Luckly or unlucky for me I left the tap on lastnight so this morning I have a complete water change .My pump works 24/7.
My ph reads 10.7the NH3/4 --------0.N2----0 N3----0.I have a gh& kh tester and the readings are off the scale.My plants are now growing very slowly which i dont mind and later on today Ill get some goldfish and see what happens .I have no intentions of playing around with the ph,although Ill be monertring the h2o every hour.
RupertofOZ said:Ok... lets clear up a couple of definitions firstly...
Hardness is defined by two different values... carbonate hardness (kH) and general hardness (gH).... and is often expressed in tests as "total hardness"...
In many aquaria circles the terms "temporary" and "permanent" hardness are often used... but that's realy a misnomer..
"Hard" water.. such as seen when soap doesn't lather.... is general hardness... not carbonate hardness...
So what do the two terms... carbonate and general hardness.. relate to...
Carbonate hardness... is the measure of the buffering capacity of the water... the ability to resist acidification... usually Calcium Carbonate..
General hardness... is the measure of the positve mettalic ions in the water... usually Calcium, Magnesium and Iron...
(To confuse matters.. both are often expressed as a value of the amount of Calcium Carbonate content... but ignore that...
)It is possible, and often the case.. that water with a high general hardness... also has a medium to high carbonate hardness... but not necessarily so...
It is also possible for water with a general hardness to have a low pH... but very rarely... and almost artificailly...
It is virtually impossible however... for water with a high carbonate hardness... to have a low pH.... it's a basic contradiction, as the carbonate buffer is exactly what resists pH decline...
So while it's possible that your water lab test might have returned a high carbonate hardness value (kH)... or even (incorrectly) expressed the total hardness as a"kH" value...
The reality is you have "hard water"... general hardness (gH)... and only RO will fix that... but hard water isn't detremental, other than to your laundry, and/or scaling of your plumbing... and it's actually a benefit to plant growth...
You may also have a high level of carbonate hardness (kH) Colin... but if so then your pH tests are wrong... totally wrong...
It's almost impossible to have pH values that you are reporting... even with general hardness....
Something just isn't right with those test values... unless they're being influenced by external factors... chemical/acid addition... or, possibly an out of calibration RO unit...
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If that's the pH of your source water... then I'm not surprised your kH and gH are off the scale... your water is virtually soap...
How do you drink/wash/garden at all.... do you have an RO unit???
You're really going to struggle to grow anything.. indeed, even cycling will be a challenge...
I think you really need to consider collecting and using rainwater for your AP system... and probably for anything else as well...
The two pH readings you posted are/were obviously completely wrong... were you using pool strip type tests??
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Well, even with extreme hard water, the buffers can eventually be used up if you are not constantly topping up with it or changing water. And then the pH can suddenly drop.
BUT, I agree with Rupert, rain water or an RO unit might seriously help your system grow happier plants. In my location I tend to try to use rain water when I have it to top up with and then I might occasionally use my well water when I need to buffer the pH up and add calcium at the same time.
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During the day when there is sun and the plants are able to use photosynthesis, the plants use up the CO2 thus removing it from the water but at night when the plants are giving off CO2 and using the dissolved oxygen the CO2 tends to build up and give you the carbonic acid. I don't know if temperatures have much effect on it but the plants do have an effect, especially completely submerged plants like algae.
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TCL is essentially correct in relation to the oxygen/carbon dioxide interaction of photosynthesis...
The diurnal swings of pH and DO within water bodies is well documented and forms the basis of all pond based aquaculture...
And it's exactly the nature of the weak bonds of carbon dioxide and oxygen that form the basis of this cycle...
I've posted the full formulas elsewhere on this forum.. and others...
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I won't argue that it has a very week acid effect but I have seen marked diurnal pH fluctuations when there is a major algae bloom, to the point that I've had people tell me only that their pH was low in the morning and high in the late afternoon and when I asked if their water was green or if there was a major algae bloom going on, the answer has so far always been yes.
Only other things I know to make pH fluctuate has to do with people adding acid to a heavily buffered system or cycles of adding either hard or acidic water to a system.
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