pH dropping off after adding CO2 scrubber and upgrading skimmer pump

[dtruitt]

pH was running a little low around 7.8 with skimmer intake plumbed outside. Drops as far as 7.65 weren't uncommon.

I added a CO2 scrubber last Friday in the hopes it would be easier for the skimmer to pull air through a shorter run to the CO2 scrubber. I saw a marginal improvement up to a peak of 7.95 (pictured) on Sunday.

That tapered off to 7.8 on Monday.

I swapped frags for a PSK 1000 yesterday. I was hoping the bigger pump would push more air. I dropped the water level and opened the outlet on the skimmer all of the way to make it as "dry" as possible. There have been a few overflows as the pump is breaking in, but the skimmate is starting to look better.

This morning around 4am, I saw the usual +0.05 bump when the lights go on, the usual -0.05 dip when the lights go off at 10am, and then at 4 pm when the lights kicked back on the pH plummeted from 7.8 to 7.7 while the lights were on from 4pm to 10pm.

Alk was steady at 9.0 both when I tested at 11am and just now at 11 pm.

Any thoughts how increasing aeration with a CO2 scrubber installed could translate to a DIP in pH while lights are on?

I dose 40mL of vinegar as an organic carbon source during each 12 hour 'day' for the tank. It's been this way for many months without any dips during light hours. It's a 65g tank.

Could the skimmer overflowing have let things back into the water that may have jacked up the pH?

 

[Reefing Madness]

 

[dtruitt]

Screenshot of pH trend in fusion is attached.

 

[Randy Holmes-Farley]

All of the pH values look low, and while they may be accurate, I would try aerating a cup of water with outside air and see if the pH ends up where it is expected. That's one of the reasons for doing my aeration test (posted below).

FWIW, electrical interference from lights sounds likely, if the "bump" you are seeing at lights on and off is as rapid as it sounds. If it is taking hours, then that is more normal..

pH And The Reef Aquarium
http://www.reefedition.com/ph-and-the-reef-aquarium/

The Aeration Test

Some of the possible causes of low pH listed above require an effort to diagnose. Problems 3 and 4 are quite common, and here is a way to distinguish them. Remove a cup of tank water and measure its pH. Then aerate it for an hour with an airstone using outside air. Its pH should rise if it is unusually low for the measured alkalinity (Figure 2). Then repeat the same experiment on a new cup of water using inside air. If its pH also rises, then the aquarium’s pH will rise simply with more aeration because it is only the aquarium that contains excess carbon dioxide. If the pH does not rise in the cup (or rises very little) when aerating with indoor air, then that air likely contains excess CO2, and more aeration with that same air will not solve the low pH problem (although aeration with fresher air should). Be careful implementing this test if the outside aeration test results in a large temperature change (more than 5°C or 10°F), because such changes alone impact pH measurements.

 

[dtruitt]

All of the pH values look low, and while they may be accurate, I would try aerating a cup of water with outside air and see if the pH ends up where it is expected. That's one of the reasons for doing my aeration test (posted below).

FWIW, electrical interference from lights sounds likely, if the "bump" you are seeing at lights on and off is as rapid as it sounds. If it is taking hours, then that is more normal..

pH And The Reef Aquarium
http://www.reefedition.com/ph-and-the-reef-aquarium/

The Aeration Test

Some of the possible causes of low pH listed above require an effort to diagnose. Problems 3 and 4 are quite common, and here is a way to distinguish them. Remove a cup of tank water and measure its pH. Then aerate it for an hour with an airstone using outside air. Its pH should rise if it is unusually low for the measured alkalinity (Figure 2). Then repeat the same experiment on a new cup of water using inside air. If its pH also rises, then the aquarium’s pH will rise simply with more aeration because it is only the aquarium that contains excess carbon dioxide. If the pH does not rise in the cup (or rises very little) when aerating with indoor air, then that air likely contains excess CO2, and more aeration with that same air will not solve the low pH problem (although aeration with fresher air should). Be careful implementing this test if the outside aeration test results in a large temperature change (more than 5°C or 10°F), because such changes alone impact pH measurements.

The "bump" usually happens over the course of one to two hours. The counter lit fuge seems very effective at keeping typical pH swing due to respiration below 0.1 pH units.

I'll have to do the aeration test with the new gear installed.

It's certainly possible the probe was incorrectly calibrated. I'll get some calibration fluid.

Electrical interference is an interesting idea. A yellow Tang that I added last night was swimming well and pecking at nori when the lights went out, but was mysteriously dead this am. Possibly a point in favor of this suggestion. I'll break out my fluke to check for stray voltage when I get home.

 

[dtruitt]

All of the pH values look low, and while they may be accurate, I would try aerating a cup of water with outside air and see if the pH ends up where it is expected. That's one of the reasons for doing my aeration test (posted below).

FWIW, electrical interference from lights sounds likely, if the "bump" you are seeing at lights on and off is as rapid as it sounds. If it is taking hours, then that is more normal..

pH And The Reef Aquarium
http://www.reefedition.com/ph-and-the-reef-aquarium/

The Aeration Test

Some of the possible causes of low pH listed above require an effort to diagnose. Problems 3 and 4 are quite common, and here is a way to distinguish them. Remove a cup of tank water and measure its pH. Then aerate it for an hour with an airstone using outside air. Its pH should rise if it is unusually low for the measured alkalinity (Figure 2). Then repeat the same experiment on a new cup of water using inside air. If its pH also rises, then the aquarium’s pH will rise simply with more aeration because it is only the aquarium that contains excess carbon dioxide. If the pH does not rise in the cup (or rises very little) when aerating with indoor air, then that air likely contains excess CO2, and more aeration with that same air will not solve the low pH problem (although aeration with fresher air should). Be careful implementing this test if the outside aeration test results in a large temperature change (more than 5°C or 10°F), because such changes alone impact pH measurements.

I saw normal induced voltage in the tank (<40VAC). I added a ground probe with no luck.

I just got calibration fluid, I will re calibrate tomorrow am.

Do you have any suggestions for placement of probes? I wouldn't want to put the probes in the sump compartment as micro bubbles / the heater so close by could easily affect readings.

Probes are currently in the refugium. This seems to work alright, as water flows from DT directly into the refugium. I would expect this would provide fairly accurate readings for temperature, but I'm unsure

All of the pH values look low, and while they may be accurate, I would try aerating a cup of water with outside air and see if the pH ends up where it is expected. That's one of the reasons for doing my aeration test (posted below).

FWIW, electrical interference from lights sounds likely, if the "bump" you are seeing at lights on and off is as rapid as it sounds. If it is taking hours, then that is more normal..

pH And The Reef Aquarium
http://www.reefedition.com/ph-and-the-reef-aquarium/

The Aeration Test

Some of the possible causes of low pH listed above require an effort to diagnose. Problems 3 and 4 are quite common, and here is a way to distinguish them. Remove a cup of tank water and measure its pH. Then aerate it for an hour with an airstone using outside air. Its pH should rise if it is unusually low for the measured alkalinity (Figure 2). Then repeat the same experiment on a new cup of water using inside air. If its pH also rises, then the aquarium’s pH will rise simply with more aeration because it is only the aquarium that contains excess carbon dioxide. If the pH does not rise in the cup (or rises very little) when aerating with indoor air, then that air likely contains excess CO2, and more aeration with that same air will not solve the low pH problem (although aeration with fresher air should). Be careful implementing this test if the outside aeration test results in a large temperature change (more than 5°C or 10°F), because such changes alone impact pH measurements.

I saw normal induced voltage in the tank. Added a grounding probe, didn't see any changes in pH probe reading.

I recalibrated the probe and I'm seeing a reading of around 8.2 now. This would make sense. Still a touch on the low side, but not unthinkable.

Im still a little perplexed by the trend which I saw, but I suppose there's no imminent threat to the well-being of the tanks inhabitants.

I still need to do the aeration test, but it may be tricky since the colder air outside may sway the results.

 

[John Rebman]

You should not be anywhere near 40VAC if your ground probe is properly grounded. My ground probe lowers my induced voltage to millivolts. Check your ground probes resistance to ground. I had a problem with salt creep causing my outlet ground to be high resistance. Cleaning outlet and cleaning ground probe brought everything back to less than 1VAC.
I found the problem in a shocking way (literally).
High induced voltage make my yellow tang hyper.

 

[dtruitt]

You should not be anywhere near 40VAC if your ground probe is properly grounded. My ground probe lowers my induced voltage to millivolts. Check your ground probes resistance to ground. I had a problem with salt creep causing my outlet ground to be high resistance. Cleaning outlet and cleaning ground probe brought everything back to less than 1VAC.
I found the problem in a shocking way (literally).
High induced voltage make my yellow tang hyper.

40VAC was before adding a ground probe. Haven't measured since. Ultimate issue was a pH probe that needed to be recalibrated, and no other issues that warranted further investigation of induced voltage as a cause for concern.