Suddenly low(er) ph....baffled

amcvay

Community Member
Review score
+0 /0 /-0
View Badges
Joined
Feb 12, 2020
Messages
35
Reaction score
9
Review score
+0 /0 /-0
Rating - 0%
0   0   0
Hello, I have a 150 gallon tank with 34 g sump. I run an Apex monitor w/PH probe. My ph is typically on the higher side of normal...8.4 to 8.5 even at it's peaks. The lows were usually 8.2 to 8.3. Several reasons for this...I have a fresh air system that replaces the air in my whole house by exchanging the heat/cool with fresh air. I have my HRV set to run 80% of the time. Upstairs (ranch house, tank is in the basement) the CO2 concentration is 420 ppm give or take. I also run a CO2 scrubber and I found the media never changes from white to purple like you'd usually expect.

So two weeks ago my PH probe is reading off the charts, 8.6...so I figure it's time to replace the probe. But just before I did that, I calibrated the probe in 7.0 and 10.0 solution. It read them both spot on. So then I ran the Apex auto calibration...ever since I did this, the ph has read low....in the high 7's and barely will crack 8.0. So I bought a new PH probe. Calibrate it and it's the same thing....low 8 at the highest. So I do a large water change to see if that may be the issue....no change.

I also run a refugium...now I would think with an HRV running 80% of the day brining in fresh air to the entire house, CO2 levels at or near outside air, a CO2 scrubber on my Deltec SC2060, AND a refugium, my Ph should never dip below 8.2.

Could all this be PH Monitor related? I haven't checked my skimmer's intake but I hear it running and I can hear it pulling in air from the CO2 scrubber.

BRS advised if my Calc was too high it may interfere with the monitor readings...that's why I did the large water change. My Hanna multi checker said Calc was over 600...but I don't really trust it.

Salinity - 1.025
Alk - 8.0
Calc - 600+ (don't believe this)
Mag - 1650
Temp - 77

Mixed reef with mostly SPS, some LPS. 22 fish...lots of flow...1 large Gyre and 3 MP40's.

The only change I made was adding Rowaphos in a bag at the mechanical filtering area....I've since removed it and Ph hasn't changed in several days.

I'm also re-checking Cal and Mag with Salifert Test Kits to get accurate readings. I wouldn't think my 50% water change with Instant Ocean would result in Calc over 600ppm???
 
Zoanthids.com

Timfish

Crusty Old Salt
Review score
+0 /0 /-0
View Badges
Joined
Jul 22, 2012
Messages
2,925
Reaction score
3,823
Review score
+0 /0 /-0
Location
Austin, TX
Rating - 0%
0   0   0
Beside wondering if there is an isssue with the testers I would wonder if there was something that has caused a change in the corals feeding and growing that has a primary or secondary effect of increasing CO2 in the system. Have you seen a rise in alkalinity over the same time frame which might be indicative of corals reducing growth?
 
World Wide Corals

Saltyanimals

Well-Known Member
Review score
+0 /0 /-0
View Badges
Joined
Jun 4, 2016
Messages
834
Reaction score
379
Review score
+0 /0 /-0
Rating - 0%
0   0   0
I’m equally baffled at my recent low pH situation as well with a very similar background. I had good healthy numbers that were solid then decided to calibrate my probe. This lead to almost your exactly range which sent me down this research path stumbling into your case. I though maybe it was a probe issue and recalibrated it 3-4 times. Eventually resigned in more calibrations when I was able to place the probe in the 2 solution packets hours later for an accurate pH based on the solution packets respectively. It’s not the probe. It’s really my tank. It couldn’t have been a overnight issue so my tank had really been at that pH for months now. Things are growing so I’m not doing anything drastic chasing this number just yet. Admittedly the whole 7.5 pH can melt coral does make me concern but haven’t seen anything melt just yet. My scrubber never changes colors, but I’ll change it again today just in case. Opening windows does increase it, but yet to cross the 8.0 mark.
 

Randy Holmes-Farley

Reef Chemist
Review score
+0 /0 /-0
View Badges
Joined
Sep 5, 2014
Messages
55,929
Reaction score
49,328
Review score
+0 /0 /-0
Location
Arlington, Massachusetts, United States
Rating - 0%
0   0   0
Things are growing so I’m not doing anything drastic chasing this number just yet. Admittedly the whole 7.5 pH can melt coral does make me concern but haven’t seen anything melt just yet.

Melt is an inappropriate description, but slowly dissolve, yes. The lower the pH, the faster it might dissolve once you get below about pH 7.7.
 

arking_mark

Valuable Member
Review score
+0 /0 /-0
View Badges
Joined
Mar 2, 2016
Messages
2,409
Reaction score
1,677
Review score
+0 /0 /-0
Location
Potomac
Rating - 0%
0   0   0
Best way to test your probe, in my opinion, is a cup aeration test. This provides a real-world assessment of your probe.

Since most probe's accuracy is at best +/- 0.1, a good enough probe should read between 8.1 and 8.5 depending on your dKH.

A tank with 7dkh should read 8.22
A tank with 8dkh should read 8.27
A tank with 9dkh should read 8.31
A tank with 10dkh should read 8 35
A tank with 11dkh should read 8.38
 
BRS

How do I get smarter in the hobby?

  • Experiment with reefing

    Votes: 167 56.6%
  • Read books

    Votes: 115 39.0%
  • Subscribe to magazines

    Votes: 58 19.7%
  • Read Reef2Reef

    Votes: 229 77.6%
  • Talk to other reefers

    Votes: 167 56.6%
  • Watch YouTube videos

    Votes: 197 66.8%
  • Listen to podcasts

    Votes: 74 25.1%
  • Other

    Votes: 22 7.5%
NooPsyche CORAL LIGHT
Top