pH aeration test question

[Miami Reef]

My pH was reading 8.25. I haven’t calibrated it in a while.

I calibrated it with a Milwaukee 7 and 10 solution, and my aquarium pH reads 7.8.

I calibrated it again with another set of Milwaukee, and the pH also reads 7.8

I then purchased Pinpoint pH solutions from Amazon and calibrated it a 3rd time, and it still read 7.8.

I was pretty thorough with the calibration process:

Rinsed probe with RO/DI and shook off excess water

Placed pH probe packets in tank water to get a temp of 77F

Placed probe in 7pH buffer solution.

Rinsed in a new cup of RO/DI water.

Shook, then placed in pH 10


Then I double checked both packets to see if they matched. The 10 pH matched perfectly, but the 7 pH showed about 6.8 (I rinsed in RO/DI before placing in the 7 to double check.




I took a cup of tank water (8dKH) and aerated it with an airstone outdoors for 1 hour.

The pH rose from 7.8 to 8.0


Does this seem correct? I don’t know. I’m still skeptical about my pH being this low lol.

 

[Garf]

My pH was reading 8.25. I haven’t calibrated it in a while.

I calibrated it with a Milwaukee 7 and 10 solution, and my aquarium pH reads 7.8.

I calibrated it again with another set of Milwaukee, and the pH also reads 7.8

I then purchased Pinpoint pH solutions from Amazon and calibrated it a 3rd time, and it still read 7.8.

I was pretty thorough with the calibration process:

Rinsed probe with RO/DI and shook off excess water

Placed pH probe packets in tank water to get a temp of 77F

Placed probe in 7pH buffer solution.

Rinsed in a new cup of RO/DI water.

Shook, then placed in pH 10


Then I double checked both packets to see if they matched. The 10 pH matched perfectly, but the 7 pH showed about 6.8 (I rinsed in RO/DI before placing in the 7 to double check.




I took a cup of tank water (8dKH) and aerated it with an airstone outdoors for 1 hour.

The pH rose from 7.8 to 8.0


Does this seem correct? I don’t know. I’m still skeptical about my pH being this low lol.

Does seem a little low. If you’ve got some Borax you could give this a whirl;

Aquarium Frontiers Biochemistry of Aquaria

 

[taricha]

Check this...
Thread 'CO2SYS Marine Tank Table for PH/DKH/CO2' https://www.reef2reef.com/threads/co2sys-marine-tank-table-for-ph-dkh-co2.786401/

Those numbers don't have to be too far off.
If your alk were actually 7 instead of 8 and the outdoor equilibrium pH 8.2 instead of 8.0, then yes that checks out.

 

[Miami Reef]

I’m all about accuracy. I tested the alk with salifert and Red Sea kits. Do you think it’s possible to have an alk of 7dKH despite them both reading around the same?

I was tempted to slightly raise the ask around 8.5-9 to counteract the low pH, but my tank is ULNS, and I don’t want to risk harming the corals. I don’t plan to mess with the alk. 7-8dKH is my target.

I think the first step is to make sure the readings are correct before I make any changes to the aquarium chemistry. I’m going to make the borax solution tonight and see what it reads.

If anyone else has any theories I’d love to hear them. I do want to fix the low pH issue. I opened all the windows, and the pH is unchanged. It’s no wonder since heavily aerating a cup outside gave poor gains.

I’m really skeptical that my pH is actually 7.8. It went down to 7.79 at night.

To put in perspective, I only dose sodium hydroxide for alkalinity. I don’t remember seeing the pH this low before. The “problem” only started after recalibrating the probe. I did rinse the probe in a muriatic acid about a week before I calibrated it with the Amazon Pintoint pH solutions.

 

[Miami Reef]

I meticulously made the borate solution. It read pH 9.0. It should have read 9.18

I recalibrated my probe again with American Marine solutions, and it only rose by 0.02. It read 8.0 exactly. But this is during peak photosynthesis. It should be higher IMO.

I bought a new double junction pH probe from BRS. I would really like to get the Thermo (Orion) pH calibration packets. I’ll try to find them online.

 

[taricha]

Like I said, 0.2 error in pH and 1 dKH error are totally plausible.

If it makes you feel better, pH is the one measure above all others that gives me trust issues.

 

[Miami Reef]

Like I said, 0.2 error in pH and 1 dKH error are totally plausible.

If it makes you feel better, pH is the one measure above all others that gives me trust issues.

I agree. pH is a fickle beast. Especially since calibration packets cannot be easily tested for accuracy, and they are very unstable. I dislike pH testing.

One part of me just wants to unplug the probe completely and just not worry about pH anymore, but another part of me really wants to know where it is at all times. It’s a good insurance policy is my ATO just stops working while I’m traveling lol. I also care about maximizing coral growth as best as possible. :)

 

[Randy Holmes-Farley]

How long did you wait for the probe to stabilize in each fluid? It can take a while. Longer can’t really hurt.

 

[Miami Reef]

How long did you wait for the probe to stabilize in each fluid? It can take a while. Longer can’t really hurt.

About 30 seconds to a minute. I did it until the Apex told me it was done. I’m pretty sure once it says it’s done it’s done, no?

 

[Garf]

About 30 seconds to a minute. I did it until the Apex told me it was done. I’m pretty sure once it says it’s done it’s done, no?

Does the Apex not allow you to fiddle with the actual reading? I’ve bought the wife the junior for her tank for Christmas so am curious. Cheers

 

[Miami Reef]

How long did you wait for the probe to stabilize in each fluid? It can take a while. Longer can’t really hurt.

Does the Apex not allow you to fiddle with the actual reading? I’ve bought the wife the junior for her tank for Christmas so am curious. Cheers

I think the probe itself might be broken. It read the pH of the 10 solution as 10.4 even though I just calibrated it again.

I ordered another double junction probe anyway. The apex has a manual calibration feature where you can wait for the number to settle, but it doesn’t allow you to input specific numbers (if your pH solution was 9.5, for example).

 

[thatmanMIKEson]

About 30 seconds to a minute. I did it until the Apex told me it was done. I’m pretty sure once it says it’s done it’s done, no?

my contribution: the alkatronic has a countdown from 120seconds but I usually float it in the calibration fluid for 30-60 seconds before starting the calibration.

also I see recommendations to use tap water on PH probes vs r.o water. I'm guessing that's from the ph difference, but idk.

I also start calibration low with 4 then 7 then finish with 10 not sure that makes a difference but ph honestly doesn't do much for me, only recently did I start monitoring it and it's never held me back before it's not going to start making the decisions for me now ;)

I'm in the same PH range:)

 

[Doctorgori]

I think the probe itself might be broken. It read the pH of the 10 solution as 10.4 even though I just calibrated it again.

I ordered another double junction probe anyway. The apex has a manual calibration feature where you can wait for the number to settle, but it doesn’t allow you to input specific numbers (if your pH solution was 9.5, for example).

pardon the deviation but while we are at it; how often do you change probes or how long do you trust one?
which brand/type

 

[Garf]

trust one?

I certainly would never trust dosing Kalk with one, let’s put it like that, lol

 

[X-37B]

I would get a hand held ph meter for reference. I have several.
I use bottled solutions for calibration.
I have an old Hanna ph/tds meter that is still going strong after 10+years with the same probe.
Keep them wet.
It does take twice as long to stabilize vs my others.
I do not run an apex but use their probe. I have a new apex probe in a box thats 4+ years old.
I check them a few times a year to make sure they are still in solution.

 

[Malcontent]

I use individually sealed, single-use tablets that make 20 mL of buffer solution each. Shelf-life is much longer, obviously.

 

[Randy Holmes-Farley]

I’d wait longer if you can. Maybe 5 minutes.

 

[Miami Reef]

I’d wait longer if you can. Maybe 5 minutes.

Hi Randy,

I received the new pH probe and calibrated it. I’m making a new pH solution of borax that Garf posted in this thread.

Just like last time, there is undissolved borax granules that take a very long time to dissolve. Should I worry about these last grains to dissolve before testing the probe’s accuracy?

Also, I used new RO/DI (from the spout) to make this and the last solution because I don’t want CO2 which can alter the final pH of the solution.

 

[Miami Reef]

This is the undissolved grains.

 

[Randy Holmes-Farley]

I think that is ok. Not sure why it is there.

Craig Bingman talks about that standard here;

Aquarium Frontiers Biochemistry of Aquaria

It also turns out that the pH of borax solutions is only weakly dependent on the concentration of borax in the solution. So, we don’t need to be tremendously precise in our measurement of the borax to still produce a useful pH standard.