Rising pH

[JulesH]

Hi, I run a mixed reef lagoon tank. I have been running Kalkwasser coming up to a year now. The Kalk stirrer is turned on when the pH drops below 8.3. I am fastidious with my checking/calibration of the Neptune Apex pH probe, so I am fairly happy that I am getting correct value to two sig figs.

However the thing that concerns me is the level that my pH climbs to during the day. As you can see from the example below I am up to 8.7 sometimes, most of the time it peaks around 8.6. The stirrer is off so this increase of pH must be due to photosynthesis?

Should I be concerned with these levels, I dont see any detrimental effects on the animals in the tank?

 

[Randy Holmes-Farley]

I’m suspicious about the accuracy of pH 8.7, but if real, there is concern about abiotic precipitation of calcium carbonate.

If it is real, increased aeration will lower it.

 

[mook1178]

I agree with Randy that you are getting into the ranges of calcium carbonate precipitation. If you can check against another pH probe, do that. pH in the marine system is mainly controlled by the carbonate system. Adding CO2 through aeration would help. Also your Calcium and alkalinity levels will help us determine if 8.7 is the real pH.

Do you have a refugium full of beneficial algae that would be drawing your CO2 levels down during the day? Can you remove some if you do?

Even if the probe is bad the swing in pH is most likely real. I feel like a swing of 0.4 pH is a lot and not a stable system. I may be wrong on that though for aquaria. I am new to the hobby, but well versed in carbonate chemistry.

 

[Gill the 3rd]

I would double check your PH readings. I would constantly calibrate my apex PH probe but it was always not reading correctly when I would compare it to my hanna and red sea kits. Those PH probes can be very finicky.

 

[JulesH]

Everyone thanks for getting back.

I have done a comparison with another pH probe. I find that both probes follow each other with the Apex probe reading high. They both calibrate in their respective solutions (Apex - 7 and 10, Reeffactory 4 and 7). I am not sure why reef factory use 4 and 7 as calibration standards as they don't match what will be measuring?

My average Alk during the day is 8.0 whilst my average Ca is 450 over a month.

 

[Gill the 3rd]

That's interesting. Based on the graph, my guess is your apex ph probe is running high. Its been awhile since I sold my apex unit, but I think my PH probe also showed higher readings than I was getting from other test kits. The reef factory and your median graph are more inline with what you should expect to see. Do you have another way to test PH to see what they are reading? I think the red sea, salifert, etc ph test kits are pretty inexpensive and can at least help verify which probe is more accurate.

 

[mook1178]

With your calcium staying steady, i would say that the Apex probe is reading high.

@Randy Holmes-Farley Do you know the solution used in the Apex calibration liquid? Is it a seawater matrix?

 

[jda]

When the probes start to go bad, they calibrate and then lose it very quickly.

I have been an advocate for years of not trusting a pH probe to dose anything or take action. With the potency of kalk, you would be better off dosing it on a timer than with a pH probe.

If the night time pH of 8.2 or 8.3 is real, I would find a different way to supplement carbonate and calcium.

 

[Randy Holmes-Farley]

With your calcium staying steady, i would say that the Apex probe is reading high.

@Randy Holmes-Farley Do you know the solution used in the Apex calibration liquid? Is it a seawater matrix?

I do not recall.

 

[mook1178]

I do not recall.

OK. I have not used it so I was not sure. I see that most of the probes used are glass electrode and salinity affects a glass electrode ionic activity. I am guessing that the calibration fluid is probably NBS solution and not a TRIS solution.

 

[Randy Holmes-Farley]

OK. I have not used it so I was not sure. I see that most of the probes used are glass electrode and salinity affects a glass electrode ionic activity. I am guessing that the calibration fluid is probably NBS solution and not a TRIS solution.

I believe the reef hobby generally uses NBS pH calibration fluids. I certainly did.

 

[Oiseaufeu]

I have the hardest time to keep my ph at 8.2. It got down several months ago and I have no corals at the moment and won’t have any if I can’t correct this. I started to open my windows for a couple of minutes every morning. Not sure how long each day I’ll need to do it, but a short period is what I would prefer as it’s winter where I live.

 

[mook1178]

I have the hardest time to keep my ph at 8.2. It got down several months ago and I have no corals at the moment and won’t have any if I can’t correct this. I started to open my windows for a couple of minutes every morning. Not sure how long each day I’ll need to do it, but a short period is what I would prefer as it’s winter where I live.

Try running your aeration line to your attic or outisde

 

[Oiseaufeu]

Try running your aeration line to your attic or outisde

Thanks! Well, I have windows directly on my roof that provide good aeration in summer.

 

[JulesH]

Randy

How would abiotic precipitation of calcium present itself in the aquarium please?

This issue I have had pH has been ongoing for a while, I have not been convinced about the any of the results from both of my pH probes.

Are there any chemical based pH test kits that could give a more reliable result, and then I should have an idea of where I am. Having said that, I would not want to get three different results!

 

[Randy Holmes-Farley]

Randy

How would abiotic precipitation of calcium present itself in the aquarium please?

This issue I have had pH has been ongoing for a while, I have not been convinced about the any of the results from both of my pH probes.

Are there any chemical based pH test kits that could give a more reliable result, and then I should have an idea of where I am. Having said that, I would not want to get three different results!

Hardening sand and collection on pump impellers, but IMO it always happens to some extent and often goes unnoticed.

 

[mook1178]

CaCO3 is a white crystal and it would concrete your sand together.

 

[Oiseaufeu]

Hardening sand and collection on pump impellers, but IMO it always happens to some extent and often goes unnoticed.

Could that explain the noise my 207 canister filter is doing intermitently now? I've been dealing with weird noises for months and I clean my canister filter regularly.

 

[Randy Holmes-Farley]

Could that explain the noise my 207 canister filter is doing intermitently now? I've been dealing with weird noises for months and I clean my canister filter regularly.

I’d open the impeller and look. Warm objects like heaters and pump impellers are more prone to deposition for a couple of chemical reasons.

 

[Oiseaufeu]

I’d open the impeller and look. Warm objects like heaters and pump impellers are more prone to deposition for a couple of chemical reasons.

I did this twice in the span of a week. My heater has some weird fluff at the bottom of it and a spot of tuffed algae on. I guess that I need to clean my filter every week or 2 when I do a water change.