Maintaining PH ..!!

[reefandfish]

I can't keep my PH up ! .... my alk is 8, calcium is 450, magnesium is 1320 and my calcium is going from 7.64/night to 7.88/day. any ideas how can i keep my PH stable somewhere over 8.0 at least during day ? I even open my windows everyday. but it still won't help much.

[crvz]

first, tell us how you're measuring pH. That's never simple, and your problem could easily be as simple as an uncalbirated/expired pH probe. If you're using a test kit, just throw it away.

Second, why do you want pH higher? Are you noticing a negative affect on your tank that you think is related to pH? Most of the time, there's nothing to worry about with pH.

[tdwyatt]

Originally Posted by crvz

first, tell us how you're measuring pH. That's never simple, and your problem could easily be as simple as an uncalbirated/expired pH probe. If you're using a test kit, just throw it away.

Second, why do you want pH higher? Are you noticing a negative affect on your tank that you think is related to pH? Most of the time, there's nothing to worry about with pH.

A smart man posted that;

Treat the patient, not the symptoms.

[tdwyatt]

btw, it you want to see if your pH probe is measuring correctly, search for the Borax test and perform it with your setup.

If you're using strips or any color match-method (unless you are using the expensive lab quality dip strips with enclosed standards strips), plan on anywhere from 10-30% (or more if they are expired) error.

More often than not, unusual pH readings with no sign of distress in the creatures in the tank indicates a need to clean yer probe and to recalibrate.

[reefandfish]

I have calibrated probe recently and its a new probe too... I have two of them controling them using AC III both probes showing about the same....

I just though that my PH should be closer to 8.0 or higher ...

[tdwyatt]

Originally Posted by reefandfish

I have calibrated probe recently and its a new probe too... I have two of them controling them using AC III both probes showing about the same....

I just though that my PH should be closer to 8.0 or higher ...

so do the borax test...

If it is spot on, the issue becomes that your tank has begun to act as an accumulating sink for CO2, and the measurements may just reflect an issue with high atmospheric CO2 in your home due to being closed up as already mentioned above for the season. If you have adequate alkalinity, and your pH probe has passed the borax test (so we make sure that the issue is not a measurement error it the probe, and this can occur even with a calibrated probe, do the borax test), the accumulation of CO2 has a measurable effect, as shown in the chart below. It may require that you run a hose outside and place a filter tip on it to bring in outside air to your skimmer for low CO2 air intake for your foam. Many threads here on the filter tip, and easy to make device with GAC in it and some filter floss or polyester fiberfill.

Below is a chart for the CO2 concentration determination based on what the actual measured pH via probe of the water column is and the corresponding alkalinity:


Ratio pCO2 For ASW compared to NSW
VALUE IN CHART IS COMPARED TO A VALUE OF 1 FOR nsw AT SEALEVEL, OR x:1

Total Alkalinity (AT)
(mEq/l) . . . 2.0 .. 2.5 .. 2.6 .. 3.0 .. 3.5 .. 4.0 .. 4.5 .. 5.0 ... 5.5 ... 6.0
(dKH) . . . . 5.6 .. 7.0 .. 7.3 .. 8.4 .. 9.8 . 11.2 . 12.4 . 14.0 . 15.4 . 16.8
pH __________________________________________________ _________
7.7---------3.0 .. 3.7 .. 3.9 .. 4.5 .. 5.3 .. 6.0 .. 6.8 ... 7.5 ... 8.3 ... 9.1
7.8---------2.3 .. 2.9 .. 3.0 .. 3.5 .. 4.1 .. 4.7 .. 5.3 ... 5.8 ... 6.4 ... 7.O
7.9---------1.8 .. 2.2 .. 2.3 .. 2.7 .. 3.1 .. 3.6 .. 4.0 ... 4.5 ... 5.0 ... 5.4
8.0---------1.3 .. 1.7 .. 1.8 .. 2.0 .. 2.4 .. 2.7 .. 3.1 ... 3.4 ... 3.8 ... 4.1
8.1---------1.0 .. 1.3 .. 1.3 .. 1.6 .. 1.8 .. 2.1 .. 2.3 ... 2.6 ... 2.9 ... 3.1
8.2---------0.8 .. 1.0 .. 1.0 .. 1.2 .. 1.4 .. 1.7 .. 1.8 ... 2.0 ... 2.2 ... 2.4
8.3---------0.6 .. 0.7 .. 0.7 .. 0.7 .. 1.0 .. 1.2 .. 1.3 ... 1.5 ... 1.6 ... 1.8
8.4---------0.4 .. 0.5 .. 0.5 .. O.6 .. 0.7 .. 0.9 .. 1.0 ... 1.1 ... 1.2 ... 1.3
8.5---------0.3 .. O.4 .. 0.4 .. 0.5 .. 0.5 .. 0.6 .. 0.7 ... 0.8 ... 0.9 ... 0.9
8.6---------0.2 .. 0.3 .. 0.3 .. 0.3 .. 0.4 .. 0.4 .. 0.5 ... 0.6 ... 0.6 ... 0.7
__________________________________________________ _________

Once the total alkalinity and pH are known, the ratio between the partial pressure of CO2 due to the atmosphere on seawater and the actual dissolved C02 of the system being evaluated can be determined utilizing the above chart. With the value from the chart known, you can decide whether you need to start ventilating the tank with outside air to your skimmer (or fans to the surface or remove glass tops) to degas the CO2 content or if you need to increase your alkalinity.

For example, if your system's pH is 7.8 and your alkalinity was 2.6 mEq (7.3 dKH mEq), then the value from the chart for the amount of CO2 dissolved in the water at normal atmospheric conditions is 3.0, so your pCO2 for the tank would be 3 times what it should be for normal concentrations of CO2 in your tank due to atmospheric dissolution of CO2 in the water COMPARED TO NSW (REMEMBER, many of us run higher that NSW values for Ca and alkalinity). If later in this same tank our pH were to be 8.2 but our akalinity were 2.6 mEq (7.3 dKH mEq/l), we would know that our pH was just about right and the amount of dissolved CO2 in the water column (pCO2) would be appropriate for the conditions present in the system.


If our chart lists a value of 3.0, or 3 times the amount of dissolved CO2 in our tank water compared to NSW, we would need to make arrangements to degas the tank for CO2 (and check our delivery rate of CO2 for tanks equipped with CO2-based Ca reactors). For Tanks with CO2 reactors, if they are using a pH controller, we would prolly need to first check the calibration of the controller probe AND the tank probe, then test a second time for alkalinity.


HTH, you can take a maon jar and fill it half way with the tank water, shake it vigorously, allow the jar to remain open for 30 min or so and repeat the process once or twice, then test it again with a probe for pH vaues. Often in systems where the pH is low due to CO2 accumulations, this procedure will allow enough CO2 to degass to significantly raise the pH of the sample.

[tdwyatt]

Sorry, with the new non-specific search engine we all enjoy at trt, I didn't realize ho hard it is to find a specific thread/topic...

Before you spend a lot of time chasing the numbers, take some time to test the probe's function using sodium metaborate, even though you've already calibrated the meter.


Calibration is good, but it is always a good idea to do a separate test with the sodium metaborate (borax) to see if your meter is testing well during normal continuous usage. I read a lot of posts where folks say that they have calibrated their pH meters and followed the directions exactly, followed all the temp bath suggestions, corrected for every possible error, yet they consistently see pH values that are skewed either high or low in their aquaria based on even the new calibration. When questioned on their procedure, almost every person I have spoken with had used standards that had either expired, or been in their LFS’s shops long enough to have expired. I read with interest Craig Bingman’s posts about a similar problem with (name deleted) brand of pH calibration solution where the pH 10 standard was off by almost a full pH unit ([H+] = 1 x 10^3). Craig had purchased a few packets of this particular brand, used a lab bench pH electrode, calibrated with fresh research-quality pH standards and tested these calibration fluids. After much board discussion, Craig proposed that folks use a freshly prepared buffering solution of sodium metaborate that will always come to the same value under home conditions. This lead to the publishing of his article in Aquarium Frontiers (circa 1997?) on the use of 20 Mule Team Borax to prepare a home standard TEST solution. I would suggest that you use this procedure to make sure that your pH probe and meter are in actuality measuring what they are supposed to. I have issues with the Hanna brand of pH probe not being able to measure the same value in the sme jar more than once, but that is a separate subject.

Essentially, the process of testing your probe's ability/accuracy involves making a standard solution of borax in RO/DI water and testing the resulting solution. This solution differs from NIST standard solutions in that NIST solution standards rely on a combined solution using controlled measured amounts of an acid and its conjugate base. Usually you would need to mix precise quantities of two different compounds to make a pH standard solution in a precisely measured volume. These will have a set shelf life, and will deteriorate more rapidly if exposed to less than ideal storage conditions. Rather than try and make these lab standards (you could, if you had the precision lab ware and a troemner balances needed to measure end volume and the acid and conjugate base weights), we can use the properties of sodium metaborate in water to form these equimolar acid/conjugate bases for us (Boric acid and hydrated borate ions). This is one of the advantages of using borax as a standard.
Quote:
pH of Sodium Metaborate Standard Solution at Various Temperatures
(3.80 grams Na2BO7 10H2O/liter)

Degrees Celsius . . . Degrees Fahrenheit . . . . . . pH
0 . . . . . . . . . . . . . . 32.0 . . . . . . . . . . . . . 9.464
5 . . . . . . . . . . . . . . 41.0 . . . . . . . . . . . . . 9.395
10 . . . . . . . . . . . . . 50.0 . . . . . . . . . . . . . 9.332
15 . . . . . . . . . . . . . 59.0 . . . . . . . . . . . . . 9.276
16 . . . . . . . . . . . . . 60.8 . . . . . . . . . . . . . 9.266
17 . . . . . . . . . . . . . 62.6 . . . . . . . . . . . . . 9.256
18 . . . . . . . . . . . . . 64.4 . . . . . . . . . . . . . 9.245
19 . . . . . . . . . . . . . 66.2 . . . . . . . . . . . . . 9.235
20 . . . . . . . . . . . . . 68.0 . . . . . . . . . . . . . 9.225
21 . . . . . . . . . . . . . 69.8 . . . . . . . . . . . . . 9.216
22 . . . . . . . . . . . . . 71.6 . . . . . . . . . . . . . 9.207
23 . . . . . . . . . . . . . 73.4 . . . . . . . . . . . . . 9.198
24 . . . . . . . . . . . . . 75.2 . . . . . . . . . . . . . 9.192
25 . . . . . . . . . . . . . 77.0 . . . . . . . . . . . . . 9.180
26 . . . . . . . . . . . . . 78.8 . . . . . . . . . . . . . 9.172
27 . . . . . . . . . . . . . 80.6 . . . . . . . . . . . . . 9.167
28 . . . . . . . . . . . . . 82.4 . . . . . . . . . . . . . 9.155
29 . . . . . . . . . . . . . 84.2 . . . . . . . . . . . . . 9.147
30 . . . . . . . . . . . . . 86.0 . . . . . . . . . . . . . 9.139
35 . . . . . . . . . . . . . 95.0 . . . . . . . . . . . . . 9.081
40 . . . . . . . . . . . . . 104.0 . . . . . . . . . . . . 9.068




Characteristics of Sodium Metaborate pH Standard solution

Characteristic . . . . . . . . . . . . . . . . . . . . . . . . Value
Composition(gm Na2B4O7 10H2O/1000 ml) . . . . . . 3.80
molality (m) . . . . . . . . . . . . . . . . . . . . . . . . . . 0.01
Molarity (M). . . . . . . . . . . . . . . . . . . . . . . . . . 0.009971
pH at 25 degrees Celsius . . . . . . . . . . . . . . . . . 9.180
change in pH after dilution
to half original concentrationin water .. . . . . . . . +0.01
Temperature coef.
dpH/dt,unit degrees Celsius-1 . . . . . . . . . . . . . -0.0082


data taken from C.Bingman Aquarium Frontiers article


These tables give the properties of differing temperatures on the pH of borax (sodium metaborate) in purified water and the resulting pH, as well as the characteristics that allow us to demonstrate the relatively small change that varying the concentration of the solution has on pH when compared to the standard solution. To make the CRC textbook standard, you dissolve 3.8 grams of borax per liter water using a lab balance and a volumetric flask. Fortunately 1/2 level teaspoon of solid borax weighs just about two grams, AND the pH of borax solutions is only weakly dependent on the concentration of borax in the solution (SEE CHART), SOOOOOooooo, we don’t need to be tremendously precise in our measurement of the borax to still produce a relatively accurate pH standard. We can make a useful product here without the use of a lab balance.

Use a pint of water (473ml) and add a half teaspoon (1/2 level tsp.) of 20 Mule Team Borax to make a resultant pH standard solution with 2 gm of sodium metaborate per 473 ml or 4.3 grams of sodium metborate/litre. Mix well. Although using this method to make the standard will only result in an accuracy of about plus or minus 10% of the lab standard sodium metaborate pH calibration solution, there is such a weak dependence of pH on concentration of the solute buffer here that it is close enough for our purposes. To use this solution to check your probe, bring a freshly made batch of borax solution to aquarium temp and immerse the probe into the solution, allowing 5 minutes for final probe measurement. The meter should show a value of 9.19 + 0.02 pH units. If your value with the meter is not within range, cleaning nd recalibration of the probe are indicated. If after cleaning and recalibrating the probe with known fresh good standards your meter/probe still cannot pass this test, then it is time to either have the meter tested against a known good meter probe combination, and failing this comparison, then replacing either the probe or the entire pH meter setup. Unfortunately Hanna pH meters at hobbyist levels are notorious for drift from calibration in as little as 2 weeks of continuous use.

Chronically high pH values in marine aquaria, as opposed to chronically low pH most often due to CO2 accumulation due to either home environment or badly adjusted Calcium reactors, are more often measurement issues than anything else, although they can occur as a result of inappropriate use of buffering additives, especially high pKa products like sodium carbonate (present in varying amounts in many reef buffer builders). Use the borax to check your meter's ability to measure the correct value, and proceed from that point. If the meter is fine, folks here on the board can suggest several possible causes and some resolutions for a fix. Let us know when you've tested the meter with the borax. I saw 20 Mule Team Borax at Target in the cleaning supplies for about $3.00, its in a green box now.


HTH

[scungili]

why do you like to torture us so...

[crvz]

Originally Posted by reefandfish

I have calibrated probe recently and its a new probe too... I have two of them controling them using AC III both probes showing about the same....

I just though that my PH should be closer to 8.0 or higher ...

while generally true... there arent many good solutions to crank pH up higher without affecting other parameters of the tank chemistry. If you arent noticing anything negative in the tank, I wouldnt worry about it. If you do think there's something bad going on, I'd first try to draw in outside air for the skimmer input. That can often be a challenge, though. Option 2 for me would be a reverse photoperiod somewhere with algae. Last option would be kalkwasser, but that has many risks when used to try and boost pH.

[dacro]

+1 don't get caught up with PH numbers... Sounds like your levels are good! Teach's 90 was extremely successful for 5 years and we never once checked the PH...