Question about pH

[cas]

Thanks @crsublette

 

[Meyer Jordan]

I have experienced and observed the opposite...



I know that pH swings can also be removed even when a residual total alkalinity of 9mg/L is maintained in a RAS system... but key word here is "maintained"... as in, carbon dioxide was properly stripped and alkalinity was added upon fish feedings.

Do you have any hyperlink references that flat out states "there will be no wild pH swings if KH is over 20~30mg/L" ? I am quite curious their context in stating this...

"Aquaculture ponds should be limed to maintain an alkalinity of more than 20 mg/L as CaCO3,
and if this recommendation is followed, acid rain should not be a problem"
Pond Aquaculture Water Quality Management(Book) (Claude E. Boyd, C.S. Tucker)

http://www2.ca.uky.edu/wkrec/AlkHardness.htm

http://www2.ca.uky.edu/wkrec/LimingPondsAquaculture.htm

 

[crsublette]

"Aquaculture ponds should be limed to maintain an alkalinity of more than 20 mg/L as CaCO3,
and if this recommendation is followed, acid rain should not be a problem"
Pond Aquaculture Water Quality Management(Book) (Claude E. Boyd, C.S. Tucker)

http://www2.ca.uky.edu/wkrec/AlkHardness.htm

http://www2.ca.uky.edu/wkrec/LimingPondsAquaculture.htm

@Meyer Jordan Look at their images... Their images still denote a diurnal pH swing... which looks to be 7.5~8.5 pH swing at high alkalinity... not sure what they mean on "high alkalinity" since they do not clarify "high alkalinity" in the image

This only proves the point that wild swings are significantly reduced at more the 20 mg/L alkalinity... rather than saying diurnal swings do not happen...

2) significant rain reduced alkalinity so much that this alkalinity change allowed other variables (such as the green water algae) to create a significant diurnal pH swing event to occur and she is testing the water at different times of day.

I stated nothing about "wild pH swings".

I stated a reduced alkalinity can leave to a diurnal pH swing... your hyperlinks show still happens when alkalinity is above 20 mg/L

 

[Meyer Jordan]

@Meyer Jordan Look at their images... Their images still denote a diurnal pH swing... which looks to be 7.5~8.5 pH swing at high alkalinity... not sure what they mean on "high alkalinity" since they do not clarify "high alkalinity" in the image

This only proves the point that wild swings are significantly reduced at more the 20 mg/L alkalinity... rather than saying diurnal swings do not happen...




I stated nothing about "wild pH swings".

I stated a reduced alkalinity can leave to a diurnal pH swing... your hyperlinks show still happens when alkalinity is above 20 mg/L

Then I misunderstood your question. However, to clarify, diurnal pH swings will occur even at high Alkalinity only the pH range of the swing decreases as alkalinity increases.

I still see no evidence that alkalinity played a major role, if any, in ashirley's pH question.

 

[crsublette]

pH is a function of alkalinity and carbon dioxide. Change either one of those concentrations and the pH changes.

Now... how much of a swing there is... depends on many variables....

And... Green water algae definitely impacts both concentrations...

 

[crsublette]

pH is a function of alkalinity and carbon dioxide. Change either one of those concentrations and the pH changes.

Now... how much of a swing there is... depends on many variables....

And... Green water algae definitely impacts both concentrations...

Rain also significantly impacts alkalinity.

Ground water run off can increase alkalinity, but, 4 inches of rain directly into the pond, this definitely would lower alkalinity.

 

[crsublette]

My focus is still on the accuracy of the test results.

I agree... This is definitely possible as well due to the age of her test kits.

 

[crsublette]

For anyone curious, here is an easy experiment to do if you want to know where your water's pH starts to change from dusk till dawn (i.e., diurnal pH changing).....

if you have access to a deionized reverse osmosis (di-RO) water system. This water has zero alkalinity and a pH hovering in the low 5s. Place this di-RO water in a slow trickle into the pond and send the RO waste water to a tree or something. Take measurements of your KH once a day. Measurement of pH at dawn and at dusk. Eventually, you will know at what alkalinity your diurnal pH changes begin to occur. Mine started to occur once my alkalinity was at around 72 ppm (4*dKH) due to the large volume of string algae I had at the time along with low water circulation.

Now, I bet this would be completely different due to the significant water circulation I now have with quite minimal algae presence.

 

[Meyer Jordan]

Rain also significantly impacts alkalinity.

Ground water run off can increase alkalinity, but, 4 inches of rain directly into the pond, this definitely would lower alkalinity.

But this is not the case with this pond (see post #24 and Post #3 concerning overflow), so rain water or run-off is not a factor and needs no further discussion.

At a pH of 8.8, CO2 levels are negligible hence impact is negligible.

 

[Meyer Jordan]

For anyone curious, here is an easy experiment to do if you want to know where your water's pH starts to change from dusk till dawn (i.e., diurnal pH changing).....

if you have access to a deionized reverse osmosis (di-RO) water system. This water has zero alkalinity and a pH hovering in the low 5s. Place this di-RO water in a slow trickle into the pond and send the RO waste water to a tree or something. Take measurements of your KH once a day. Measurement of pH at dawn and at dusk. Eventually, you will know at what alkalinity your diurnal pH changes begin to occur. Mine started to occur once my alkalinity was at around 72 ppm (4*dKH) due to the large volume of string algae I had at the time along with low water circulation.

Now, I bet this would be completely different due to the significant water circulation I now have with quite minimal algae presence.

Interesting, but no real bearing on this thread.

 

[crsublette]

My pond has a raised edge so we do t get runoff from the yard.

Excellent clarification. So no concern with runoff influencing this.

 

[crsublette]

But this is not the case with this pond (see post #24 and Post #3 concerning overflow), so rain water or run-off is not a factor and needs no further discussion.

Not just the rain water that is leaving the overflow.... Actually, the water entering the overflow would be pond water at that moment, not rain water.

 

[crsublette]

At a pH of 8.8, CO2 levels are negligible hence impact is negligible.

I agree... that is when the pH is at 8.8.

 

[crsublette]

Various types of respiration (not just plant) and organic decomposition injects carbon dioxide into the water... Thus lowering the pH if alkalinity levels and water circulation are not sufficient...

Photosynthesis removes carbon dioxide and alkalinity from the water... thus increasing the pH if alkalinity, water circulation, and calcium levels are not sufficient.


Of course... I am assuming her pH tests are accurate... If they are accurate, than what I am stating is quite applicable (except for the runoff aspect that I was rightfully corrected on)....

If the pH tests are inaccurate, then @Meyer Jordan I agree that you are correct.


@ashirley will have the final say I figure upon sharing her test results, which will clarify much.

 

[crsublette]

Here is my predicton... I bet her pH test results will not be 8.8 nor 7.6.


@ashirley Would be good to test your water at dawn and again at dusk, as @Meyer Jordan suggested you to do as well. Also, will be quite interesting to know your KH levels. This will clarify much.