Pond Boss Forums GENERAL QUESTIONS Water chemistry water test

I had my pond water tested when I took pool water to be tested said PH was 6.8 (taken fron top of pond mid morning) Alkalinity 10, and calcium hardness 60. Can anyone give me pertinent info on these numbers? Pond was excavated Oct 2006 and is supplied with water from shallow water table here in JAX., FL.

Unusual results. When hardness is 60 alkalinity is usually higher than 10 ( I would guess around 25 min.) . An alkalinity of 10 is to low for a fertile pond. You need 20 at least. Ask your county ag agent about your area.

I am guessing about what is up. Two guesses. Mostly acid water in the pond (from the acid dirt) so you have a low alkalinity but the water (ground water or from a well ?)is from a Fla limestone aquifer and thus has hardness which is in the top water layer if that is where a well dumps it. Or second (I doubt this one) the pond water has natural hardness and the well/ water source has low alkalinity (acid character). See the following :

http://srac.tamu.edu/tmppdfs/13452410-46...ebb6b2d5a43a5f3

I agree with Erik, hat these is unusual results. A pH of 6.8 would not usually occur with such low alkalinity. It is possible to have a PKa "plateau" that would result in pH like this, but if that is the case, you can easily "slide" to an extremely low pH and have a fish kill.
You may be seeing the impact of organics in the water (primarily tanic acid) from decay of pine needles or oak leaves, that neutralize the carbonate and bi-carbonate alkalinity associated with calcium and magnesium hardness. This neutralization converts alkalinity to CO2 and carbonic acid. The harness will then be associated with an organic acid yet still measured as hardness. Adding ag lime will increase both hardness and alkalinity and add to the buffering of the water.
You might want to get another sample, and try to get a composite sample by taking small samples from various areas of the pond and combining them, to give you a more representative perspective.

Leaves from surounding oaks, maples, and a few pines do blow into the pond. Pond was excavated Sept. 2006. I just mailed off a water sample to Ken's Fish Farm today, hopefully they will have some answers.

In order to get a proper pH test, the water needs to be tested at the time of sampling. CO2 can either be absorbed into the water and lower pH, or be lost from the sample and raise pH. Temperature changes and biological processes in transit can change pH dramatically in low buffered waters.
To get an accurate pH, test when you sample, and take several small water samples and make a larger composite that will more accurately represent the pond as a whole.

Mike

See if your county ag agent will do a test for both the water and the pond bottom dirt (watershed).

Fla.
Univ of Fla. Ext.

http://prohort.ifas.ufl.edu/diagnostics.htm

I sent UF a sample of dirt that came from one of the piles left for us after pond was dug. The dirt in the pile is like dirt at pond bottom. Sample dirt came back PH= 4.36.
I also have water test results that say:
PH=5.0
Total hardness=17
Total alkalinity=17
Total ammonia=.36
So, expert ponder's what now?
My calculations have pond size at .159 acres and average depth of 6.55 foot.

Question:
Can I get a more accurate PH by testing samples onsite from different areas of pond and averaging them?

Yes,
On-site pH tests at various locations and depths will give more accurate picture.

I just noticed on the water test results I got that they listed pond size as 1.04 acre. My calculations have it at .159.
-The readings should not change because of this size difference should they?
-I know the recommendations given are not the same because of size difference.
-My pond is 105 X 66 and 6.55 average depth. Is my calculation correct? 105X66=6930 divided by 43,560=.159

I don't see how it could affect the test results, and your calculations look good to me.

Thank you, Have gotten lots of help here and learned alot.

Theo is right. Size of pond will not impact the water sample analysis. the smaller the pond, the more uniform the water will be across the entire water column. Other than that, once you take a sample, the water analysis reflects that water. As with any analysis, the results are only as good as the sampling technique.

In medicine (I am a physician) the first thing we do when we get a weird and self-contradictory lab test is to repeat it. You would best do this before making big plans about correcting what might be a lab error, or even a mixed up sample given the fact the area of the sample pond was not matching yours.