pH slowly dropping over the last week

[reefmaster70]

hello all. I have a question about my (3) month old 75g reef tank. So for the last 7-10 days my Apex has been setting off an alarm for low pH. To preface this, I have a 20g reef tank about 30 ft away and has a rock solid pH of around 8.1, not that it matters much, but just to give some overview of the space. Our home was built in 1979, so it's certainly not air tight, like newer homes.

Anyway, my pH in my 75g tank hit 7.49 last night after lights had been off for a few hours. I know this normally occurs with any tank when lights go out, ph tends to drop some.

The ONLY things I have changed somewhat recently in the tank are: Phosban reactor running a small amount of Phosban, as my phosphates have been running up around .30 and I want to lower them a bit more. and I have been dosing a bit of Microbacter7 to continue to add healthy bacteria to a young system, and keep unwanted algae's in check.

I am doing all the "usual" pH raising things including powerheads up at the surface agitating surface water, and breaking surface tension, I have an extended airline off of my skimmer, that runs to the outside of my stand, since the stand is pretty well sealed. and I add a bit of Kalkwasser manually daily. My Alkalinity is sitting in the 10.5dkh range.

Any help to get my pH back up to at least 8.0-8.1 would be wonderful. I am considering adding a CO2 scrubber, or at least an airstone in the display tank for a while to see if that bring it back up.

Appreciate any help.

 

[eggie]

I would try calibrating the Ph probe make sure its reading accurate

 

[reefmaster70]

I would try calibrating the Ph probe make sure its reading accurate

I am going to do that again today...as this continual drop seems "suspect" to me...I am also going to check the pH with my Hanna master test kit to get a reading. And I am also doing a 20% water change today as well.

 

[eggie]

I am going to do that again today...as this continual drop seems "suspect" to me...I am also going to check the pH with my Hanna master test kit to get a reading. And I am also doing a 20% water change today as well.

Use the Manual Calibration for the probe on the Apex
The use of GFO tends to reduce PH as well
Kalk wasser at night tends to raise it a little bit more and precipitates phosphate as well

 

[reefmaster70]

Use the Manual Calibration for the probe on the Apex
The use of GFO tends to reduce PH as well
Kalk wasser at night tends to raise it a little bit more and precipitates phosphate as well

ok, just did the manual recalibration until the meter says 100% and numbers were settled. and the probe and apex were reading 10.02 on the 10.01 solution. So I put the probe back into my sump and waited an hour and it's still reading 7.5 pH. So I assume it's now reading correctly. However i still don't like my pH that low. I just did a 20% water change today too and now my pH is reading 7.49. This crap is crazy.

 

[eggie]

Try doing the Aeration test described here
https://www.reef2reef.com/threads/understanding-ph-in-reef-tanks-part-one.1126846/

 

[Randy Holmes-Farley Verified Community Expert]

ok, just did the manual recalibration until the meter says 100% and numbers were settled. and the probe and apex were reading 10.02 on the 10.01 solution. So I put the probe back into my sump and waited an hour and it's still reading 7.5 pH. So I assume it's now reading correctly. However i still don't like my pH that low. I just did a 20% water change today too and now my pH is reading 7.49. This crap is crazy.

Water changes don't generally do much for pH.

pH is determined mathematically by the alkalinity and the CO2 in the water, and CO2 in the water is typically impacted strongly be three things: CO2 in your home air, photosynthesis (consumes CO2) and respiration (adds CO2).

Closed windows often drive down pH for this reason.

 

[reefmaster70]

just did a quick check of both my 75g and 20g tanks...both of the sitting at about 7.5 pH (just before lights come on at 10am). Alk on 75g is still at 10.5 dkh and my 20g is at 9 dkh. So alk is good on both. so not sure if I even should bother chasing pH and try and "up" it, or leave well enough alone.

 

[BonnieB]

I used to test my ph in the morning before lights on and it was always 7.8. I was a new reefer at the time. One day my LFS came over at 1 in the afternoon and it was 8.2. See if yours charges in the day and my personal and unprofessional opinion is if your tank is doing good otherwise, don’t chase this.