Cold Weather & pH

[jcook54]

It's starting to happen again, my high pH alarm is starting to go off just like it did towards the end of last winter. For some reason when the weather gets cooler, my pH climbs to 8.5+ during the light cycle. Typically the alarm will go off an hour or so before my lights kick off. Why is this happening? I haven't changed any inputs and it really does seem to be caused by cooler temps outside. The alarm went off a few weeks ago when we had 2-3 cooler nights and, after last night, the pH started quite a bit higher than it usually does. If you look at the past pH, you can see that if the day was a hot one, the pH would be lower. September 18th & 19th still had cooler night but the last few days have been really warm. I have no idea why cold weather would alter the pH so much. Has anyone experienced this?

A few things to note: 1. The tank is in a basement with lots and lots of ventilation and no conditioned air. In Winter the air temp can get be in the low 60's if it's really cold outside. 2. It has been 9 months since I calibrated my pH probe. I don't believe this is the root cause, however, because I experienced the same high pH last winter after correctly calibrating the pH probe. 3. It's a fairly large space and there's never more the one person down there (Me) and even then it's not for very long. i.e. there aren't any folks exhaling and putting CO2 into the air.

 

[chemaholic]

pH is usually temperature corrected. As the water gets colder pH will go up.

 

[Adam]

Temperature Compensation is turned on in his Apex for that probe.

I have a couple theories but they are a little out there.

 

[jcook54]

Well @Adam we've talked about this and you know as much as I do about the system. "Out there" theories are right up my alley!*


*See previous post where I'm convinced dried chicken waste shot my PO4 levels through the roof.

 

[Adam]

I know colder air is more dense. More air might mean more gas exchange.

I don't know how co2 mixes with air or if it will separate out. But denser co2 may sit closer to the floor and not get absorbed into the water column.

The 1st one is not as far out there as the latter.

The probe reading does drift up between calibration. So there's that too.

 

[chemaholic]

It is more of an effect of how fast the molecules move in the solution. Air has minimal impact on it as far as temperature goes.

 

[Jaycen B.]

Cooler air has a higher O2 concentration. That will raise PH..

 

[chemaholic]

The air will have minimal impact on the pH of a solution unless you are aerating the solution.

As the temperature of a solution increases molecules move faster. That is actually what you measure when you measure temperature. They also vibrate faster. This changes how easy it is for ionization to occur. Higher temperatures increase water molecule vibrations making it easier for them to ionize and produce H+ ions. This is the H in pH. More H+ means lower pH. The opposite is also true so lower temperatures push pH up.

 

[ichthyoid]

A few thoughts,
-In your Apex graph above, I see at least 4 small bumps in pH, at what appears to be during the morning. Is that kalk dosing, or similar? If so, why aren’t you dosing during the night, at regular intervals, so it’s available as needed. It might help flatten your curve & make things more stable.

-the pH scale is a logarithmic scale, so a change of +/- 1 means 10x as many or fewer hydrogen ions. A change of 0.5 means 5x’s etc. So, this should provide perspective on the scale of your swings (2 would mean 100x).

-you mentioned not calibrating the pH probe for 9 months & having temp. compensation on. Have you calibrated your temp. probe?

-daily swings of pH in an aquarium are mostly due to photosynthesis. Plants, including algae, have 2 mechanisms going on-
1- respiration, just like us, they take in O2 and produce CO2, during this light independent reaction. It goes on 24x7, just like us.
2- photosynthesis, occurs during periods of sufficient light. During high enough intensity, photosynthesis consumes all of the CO2 produced from plant respiration plus some additional from the environment (hence, the ‘takes up’ CO2 part). It also produces more O2 than is required by respiration (the ‘produces’ O2 part), so there is an excess. At night they still use O2 and produce CO2, without benefit of photosynthesis. Thus, at night due to respiration those same plants actually drive down pH, due to the absence of benefits from photosynthesis. The reason plants have photosynthesis at all is to produce glucose for themselves, to be used as food. These are often misstated and/or poorly understood, imo.

-the rate of reaction for photosynthesis peaks at about 68 degrees F, due to maximum enzyme activity in the biochemical processes involved (there is a lot going on). Below and above that temperature, photosynthesis slows down.

-there are many interdependent variables involved in photosynthesis, gas exchange kinetics, ion availabilities, etc. There are a lot of hysteresis effects which occur as a result.

-the Neptune Apex apparently does not average pH readings by default. So, any anomalous ‘spike’ can lead to an error being generated. I found a link which refers to this very thing, including a fix. Hope that it helps -

PH level alarm for Apex driving me nuts

So I am brand new to apex. I have an alarm set up for above 8.40 and below 7.80 to let me know. And I keep getting notifications thst is is out of the ranges. But when I look at the monitor it is never out of those ranges. What am I missing. It’s driving me nuts. Two pictures attached showing it

www.reef2reef.com

 

[chemaholic]

A few thoughts,
-In your Apex graph above, I see at least 4 small bumps in pH, at what appears during the morning. Is that kalk dosing, or similar? If so, why aren’t you dosing during the night, at regular intervals, so it’s available as needed. It might help flatten your curve & make things more stable.
-the pH scale is a logarithmic scale, so a change of +/- 1 means 10x as many or fewer hydrogen ions. A change of 0.5 means 5x’s etc. So, this should provide perspective on the scale of your swings (2 would mean 100x).
-you mentioned not calibrating the pH probe for 9 months & having temp. compensation on. Have you calibrated your temp. probe?
-daily swings of pH in an aquarium are mostly due to photosynthesis. Plants, including algae, have 2 mechanisms going on-
1- respiration, just like us, they take in O2 and produce CO2, during this light independent reaction. It goes on 24x7, just like us.
2- photosynthesis, occurs during periods of sufficient light. During high enough intensity, photosynthesis consumes all of the CO2 produced from plant respiration plus some additional from the environment (hence, the ‘takes up’ CO2 part). It also produces more O2 than is required by respiration (the ‘produces’ O2 part), so there is an excess. At night they still use O2 and produce CO2, without benefit of photosynthesis. Thus, at night due to respiration those same plants actually drive down pH, due to the absence of benefits from photosynthesis. These are often misstated and/or poorly understood, imo.
-the rate of reaction for photosynthesis peaks at about 68 degrees F, due to maximum enzyme activity in the biochemical processes involved (there is a lot going on). Below and above that temperature, photosynthesis slows down.
-there are many interdependent variables involved in photosynthesis, gas exchange kinetics, ion availabilities, etc. There are a lot of hysteresis effects which occur as a result.
-the Neptune Apex apparently does not average pH readings by default. So, any anomalous ‘spike’ can lead to an error being generated. I found a link which refers to this very thing, including a fix. Hope that it helps -

PH level alarm for Apex driving me nuts

So I am brand new to apex. I have an alarm set up for above 8.40 and below 7.80 to let me know. And I keep getting notifications thst is is out of the ranges. But when I look at the monitor it is never out of those ranges. What am I missing. It’s driving me nuts. Two pictures attached showing it

www.reef2reef.com

I am now fascinated by this puzzle.

Great information! I had not considered the impact of respiration on pH which would definitely cause pH to be lower during the day and higher at night.

Quick question about the chart. Is the tick mark with the date midnight or is the tick mark labeled 12:00 midnight? I assume the date represents midnight.

I think your first step should be to make sure your temperature probe is right next to your pH probe. Make sure there are no heaters or chiller return water near them. Make sure you are not dosing anything near them and make sure they always stay submerged. If that does not address the issue then do what was suggested above and check the calibration of both probes. Also check for drift in the measurements over time meaning put the pH probe in the calibration solution after you calibrate it and let it sit for 15 minutes or so to see if the value starts changing. This is pretty common honestly. A pH probe can easily drift .1 or .2. I have seen it in the lab many times. If it is drifting significantly then you may want to replace it. Double junction probes are the only way to go.

Do you have a temperature chart you can overlay on the pH chart? That would help you determine what impact if any temperature is having.

Another question I have is what is going on between midnight and noon that is causing the sawtooth pattern on the chart? It seems to have a regular frequency. It seems like there is about two hours between peaks. Is there dosing going on during this time say once every two hours or something? Is there an automatic water change system or ATO that is set to run at night? If the ATO or water change water is being put into the same part of the sump that the pH probe is in you might expect to see something like this.

I am excited to see what you find as you work through things!

 

[ichthyoid]

“Great information! I had not considered the impact of respiration on pH which would definitely cause pH to be lower during the day and higher at night.”

It’s the opposite, pH increases during daytime, due to photosynthesis over compensating for the effects of respiration.

 

[chemaholic]

« Great information! I had not considered the impact of respiration on pH which would definitely cause pH to be lower during the day and higher at night. »

It’s the opposite, pH increases during photosynthesis/daytime, by over compensating for the effects of respiration.

Interesting. I need to read up on that more. I assumed since the critters were putting out CO2 that you should see pH drop.

 

[ichthyoid]

Interesting. I need to read up on that more. I assumed since the critters were putting out CO2 that you should see pH drop.

You do, at night, when photosynthesis is switched off.

 

[chemaholic]

Okay it just clicked. Corals will consume CO2 during photosynthesis increasing the pH. I suppose the question in a mixed reef would be how much coral do you have compared to fish. I am not sure how plant respiration compares to fish respiration. Something else I need to read about. Thank you for the additional information!

 

[ichthyoid]

It’s not only the coral, in a healthy mature reef, we also have coralline algae all over the place. Easy to overlook-

Coralline Algae: The Unsung Architects of Coral Reefs

ocean.si.edu

 

[Adam]

I believe all for one or an alk component is being dosed at night.

The temperature of the water in the system is not changing. 77-78 degrees. What is changing is the ambient temp both outside and in his basement. There are no other changes to anything being done by him. Just cooler air that also seems to correspond to the pH going up.

 

[chemaholic]

I believe all for one or an alk component is being dosed at night.

The temperature of the water in the system is not changing. 77-78 degrees. What is changing is the ambient temp both outside and in his basement. There are no other changes to anything being done by him. Just cooler air that also seems to correspond to the pH going up.

When it is cooler the heater probably runs more often. If the pH probe is near the heater and the temperature probe is not or vice versa then you absolutely will see fluctuations in pH. This is why I mentioned the two probes need to be right next to each other and nowhere near heaters, chiller water, or dosing.

If something is being dosed near the pH probe then that will cause fluctuations in pH as well depending on what it is being dosed.

I am really interested in seeing what ends up being the cause.

 

[ichthyoid]

When do his lights come on & go off @Adam ?

 

[jcook54]

Wow! Thanks for the replies, I was fishing all day yesterday and I'll try to answer some questions.

• The 4 bumps you see are my Alk dose. I scheduled them overnight when the pH was the lowest to try and keep the swings to a minimum. That was the thinking at the time but I could change them to earlier in the night when the pH is dropping just as easily.
• Lights come on at 10:00 am, this starts the pH climb. They go off around 7:00 pm and that when the pH starts to go down. If you look at the 1 day graph, you'll note a pH plateau. That is when the T5s turn off and the LEDs are still running.
• The 4 spikes that are a result of Alk dosing happen at 2:30 am, 4:00 am, 6:15 am & 8:00 a.m. What sometimes looks like a 5th spike is the LEDs coming on at 10:00 a.m. and ramping up.
• My sump is just one big tank, no baffles, just a trough. I have a small powerhead in the sump to keep everything mixed up well. When it gets cold outside, there would be cold and hot spots in the sump and the powerhead helps prevent that. That being said, the Temp and pH probe are an inch or two apart.
• Wow. I just looked at the temp data overlayed on the pH data. When it's warmer out, they look nearly the same. If you look at the graph you'll see the last few nights have been cooler and the bottom end of the temp scale is much more jagged as the heater cycles on and off a lot more.
• The screen grab of the attached pH/Temp data lists the pH in blue and the temp in orange.
• There's a pH trough on September 24th and was caused by a water change. New water gets added to the sump so it really messes with the pH for a time before it all mixes together.
• The overlay chart shows exactly what I'm talking about. Monday, Sept. 19th was fairly cool and the pH was 8.4+. The rest of the week got progressively warmer and the pH peak went down to 8.34 before it started cooling off again on Friday at Saturday resulting on the pH peak going back up to 8.43. As the basement temp continues to cool, the peaks will get higher and higher and start to trigger alarms.
• One other thing to note, my nutrient are pretty low and I only run the skimmer at night. I could open it up and run it 24/7 and see what that does. In my head I was thinking that running the skimmer would help keep the pH up overnight and offer some stability but keeping the swing to a minimum.

This is fun and thanks for taking the time to consider what I'm dealing with. I know it's only going to get worse as the basement continues to cool.

 

[Adam]

I'm gonna go out on a limb and say the cooler temps are possibly creating more drafts, which in turn drops it co2 levels in the basement air. All while the only time skimmer is running during a 24hr period.

My unscientific thoughts have always been that the way to increase overall system pH is to control the lowest pH of the day. Raise the floor so to say, and lift the valley low to a higher plateau. This will allow the time during photosynthesis to lift it higher during the photoperiod. That is pretty much what we are seeing here.

I'm very interested in what @chemaholic & @ichthyoid have to say and what their thoughts are, as they have much more knowledge on the chemical processes.