Is adding H202 to RO water before mixing salt a viable way to increase pH?

[DaddyFish]

I run skimmerless tanks and have community well water. My incoming water is 5-stage filtered before it hits the RO membrane and finally DI. Final pH of RO is typically 7.6-ish and that's where my tanks tend to fall back to if I don't add buffer. Example tank: Alkalinity(dKH) 9.41, pH 7.6

My problem with adding buffer to increase pH is that after salt mixing my dKH is already high in the 8-10 range, so adding buffer sends it over the top (12+). CO2 is certainly a contributor because it's worse in colder weather, but opening windows and/or aerating with outside air only gains me about 0.2 increase at best. And within a couple days the pH will fall right back to the original value of the generated RO water. It's like there's something besides CO2 that's not being caught/filtered by RO that's buffering the pH into the 7.6-ish range, and dumping more chemicals into the water never seems to be a good solution for me.

I'm thinking about trying H202 in the RO water, allowing it to mix for 24-48 hours, then add salt and mix. Thoughts, suggestions? Is this just too much chasing numbers?

 

[Randy Holmes-Farley]

Many issues with this...

No, Neither oxygen nor hydrogen peroxide have anything to do with pH. It is CO2 and alkalinity that matter.

No, you cannot accurately measure the pH of Ro/DI water. pH meters fail to do so accurately. It may be a bit below 7 due to CO2 entering, but that's no real concern for the final mix.

Finally, adding pH 7.0 totally pure fresh water to seawater at pH 8.2 actually raises the pH, not lowers it. One of the quirks of chemistry.

 

[DaddyFish]

Just a moment ago I ran a 10-minute purge of the system and tested my RO/DI water pH. It's testing at 6.4 with one meter and 5.9 with another. I do understand how in the absence of any buffering the pH is nearly impossible to measure with pH meters. The 7.6 that I typically get is when I measure the pH of my mixing tank before adding salt. There's always some residue left behind in that tank and that explains the higher reading there.

If I correctly understand what you're saying, with the tank alkalinity in line/on target at 9.41, a pH reading of 7.6 means I'm dealing with a CO2 issue, plain and simple?

 

[Randy Holmes-Farley]

If I correctly understand what you're saying, with the tank alkalinity in line/on target at 9.41, a pH reading of 7.6 means I'm dealing with a CO2 issue, plain and simple?

Yes, or pH measurement error. It implies CO2 levels pretty high, which implies quite high indoor air CO2 levels. About 4x normal.

 

[DaddyFish]

Yes, or pH measurement error. It implies CO2 levels pretty high, which implies quite high indoor air CO2 levels. About 4x normal.

There was a thread a while back with an affordable but supposedly useful/effective CO2 meter listed. It was unavailable last time I looked. You wouldn't happen to have a recommendation on one would you?

 

[Randy Holmes-Farley]

There was a thread a while back with an affordable but supposedly useful/effective CO2 meter listed. It was unavailable last time I looked. You wouldn't happen to have a recommendation on one would you?

No, I've never used one, and in general, I'm not sure they are worth it for most situations. Fun, yes,. needed? No.

An aeration test on the tank water can provide rough info on the CO2 levels indoors and out:

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.

 

[DaddyFish]

No, I've never used one, and in general, I'm not sure they are worth it for most situations. Fun, yes,. needed? No.

An aeration test on the tank water can provide rough info on the CO2 levels indoors and out:

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

The Aeration Test

...

I did find that test earlier and I understand the comparison principle involved. Thanks, I'll do it!
I also located a reasonably priced CO2 meter on Amazon, not by searching but by searching through several matches on "CO2 meter" and looking at the Alternative Products listing at the bottom.

I use ventless propane gas logs for supplemental/emergency heat in my home. I have lots of CO alarms but nothing for CO2, and I know that despite avoiding the use of those logs, my fish all huddle up in November and discuss how "Winter is coming and we must be prepared!!!" I would move them outside but then they'd freeze. Short of supplemental oxygen, I'm running out of ideas.

 

[Randy Holmes-Farley]

I use ventless propane gas logs for supplemental/emergency heat in my home. I have lots of CO alarms but nothing for CO2, and I know that despite avoiding the use of those logs, my fish all huddle up in November and discuss how "Winter is coming and we must be prepared!!!" I would move them outside but then they'd freeze. Short of supplemental oxygen, I'm running out of ideas.

That will certainly send CO2 very high. Adding O2 won't help.

 

[DaddyFish]

I definitely have gas, er... a gas problem.
1-hour indoor aeration of a 1-gal bucket produced a change from 7.60 to 7.95.
Currently repeating the test with outside air for one hour.

Back with an update from second stage test using outdoor air. 1-hour aeration raised pH to 8.23.
Time to rethink my aeration setup.

 

[DaddyFish]

@Randy Holmes-Farley asking for help with testing evaluation and possible next steps.

* I tested CO2 just above one of my DTs today and it's averaging 600-700 ppm. Which I believe is considered "Poor".
* All last night I aerated a mixing tank with RO/DI that was salted very low to 1.002 so pH could be measured. Overnight it rose from 7.8 to 8.34.
* Then this morning I added more salt to that mixing tank to reach 1.025 and continued to aerate, mix and heat for roughly 8-hours. pH dropped to 7.93.
* Then I added one recommended dose of Seachem Marine Buffer 8.3 and continued to aerate, mix and heat for one hour. pH raised to 8.17, but remains very shy of the expected 8.3.

Indoor room air is well stirred and it's safe to assume that the air surrounding the mixing tank is a close match to where I tested above the DT. My goal was to determine if starting with pure, clean water and strong indoor aeration would yield a stable 8.3 pH. It has not.

My assumption is that I am battling a CO2 problem that isn't likely to go away under current conditions. My assumption is that I also could benefit from increased outside air aeration in the tanks, but using inside air is at best going to get me in the 8.1x range, so why waste time with inside air sources?

 

[Randy Holmes-Farley]

I think you are spending too much time doing things that are not useful. We know what impacts pH and how to deal with it.

Stop using Seachem Marine Buffer for anything. It cannot possibly do what it claims. Is just an ordinary alkalinity supplement with added borate that will potentially accumulate in the aquarium. The Seachem claim that it 'Maintains pH 8.3 in all marine aquariums" is just nutso.

You may get a real reading, but it is not useful to measure the pH of a low salt solution as a predictor of the pH when you add more salt. The pH changes substantially and in ways that I'm sure you would not predict. If you combine normal seawater at pH 8.1 and add totally pure fresh water at pH 7.0, the final pH will be above pH 8.1. Dilution has a big impact on the pH of seawater. That explains your RO/DI plus salt result.

Indoor air with a CO2 level of 700 ppm will lower the pH of seawater equilibrated with it by about 0.3 pH units compared to aeration with 350 ppm CO2 outside air.

I agree that your untreated indoor air is not useful for raising pH. It rarely is for an aerated reef tank. Most folks use outside air, treat their indoor air to remove CO23 (CO2 scrubber) or remove CO2 from thwe tank some other way (increased photosynthesis, kalkwasser/limewater, etc.).

 

[arking_mark]

My recent pH journey...

Kalk + Skimmer + CO2 scrubber took me from 7.8 -7.9 to 8.26 - 8.36.

Also, continually just adding a buffer (Alk) will eventually unbalance your system.

 

[DaddyFish]

I think you are spending too much time doing things that are not useful. We know what impacts pH and how to deal with it.

Stop using Seachem Marine Buffer for anything. It cannot possibly do what it claims. Is just an ordinary alkalinity supplement with added borate that will potentially accumulate in the aquarium. The Seachem claim that it 'Maintains pH 8.3 in all marine aquariums" is just nutso.

You may get a real reading, but it is not useful to measure the pH of a low salt solution as a predictor of the pH when you add more salt. The pH changes substantially and in ways that I'm sure you would not predict. If you combine normal seawater at pH 8.1 and add totally pure fresh water at pH 7.0, the final pH will be above pH 8.1. Dilution has a big impact on the pH of seawater. That explains your RO/DI plus salt result.

Indoor air with a CO2 level of 700 ppm will lower the pH of seawater equilibrated with it by about 0.3 pH units compared to aeration with 350 ppm CO2 outside air.

I agree that your untreated indoor air is not useful for raising pH. It rarely is for an aerated reef tank. Most folks use outside air, treat their indoor air to remove CO23 (CO2 scrubber) or remove CO2 from thwe tank some other way (increased photosynthesis, kalkwasser/limewater, etc.).

Thank you. This isn't the first time I've "run around guessing what's inside the box instead of reading the label and opening it".

I'm going to work on replacing indoor air with outside air and more plants as next steps.

I do appreciate your time!

 

[Randy Holmes-Farley]

Thank you. This isn't the first time I've "run around guessing what's inside the box instead of reading the label and opening it".

I'm going to work on replacing indoor air with outside air and more plants as next steps.

I do appreciate your time!

You're welcome.

Plants won't help much unless the room looks like a greenhouse.

The plants would need to add mass (tissue) in an amount similar to the amount of food you eat to offset your CO2. Then there are gas stoves and other sources.

 

[DaddyFish]

I meant aquatic plants in the tanks.

 

[Randy Holmes-Farley]

I meant aquatic plants in the tanks.

Ah, yes, that can be help. Especially in a refugium on a reverse light cycle.

 

[mdb_talon]

Finally, adding pH 7.0 totally pure fresh water to seawater at pH 8.2 actually raises the pH, not lowers it. One of the quirks of chemistry.

Example 87 of why I will never understand chemistry.

 

[Randy Holmes-Farley]

Example 87 of why I will never understand chemistry.

Even with a PhD in chemistry, that answer would not have been my first guess before looking carefully into it. lol

 

[DaddyFish]

An interesting twist to my studies. This evening with everyone else out of the house, no HVAC circulation, and presumably the air migrating up from the propane wall heater I have in the basement garage, my CO2 jumped to over 1200 and rising. I tested several areas of the main living space with similar results. The basement garage itself is in the 350 range.

@Randy Holmes-Farley Do you have a chart of sorts (to share) showing the correlation between indoor CO2 levels and pH at equilibrium, to go with this statement you made earlier?

"Indoor air with a CO2 level of 700 ppm will lower the pH of seawater equilibrated with it by about 0.3 pH units compared to aeration with 350 ppm CO2 outside air."

 

[Randy Holmes-Farley]

An interesting twist to my studies. This evening with everyone else out of the house, no HVAC circulation, and presumably the air migrating up from the propane wall heater I have in the basement garage, my CO2 jumped to over 1200 and rising. I tested several areas of the main living space with similar results. The basement garage itself is in the 350 range.

@Randy Holmes-Farley Do you have a chart of sorts (to share) showing the correlation between indoor CO2 levels and pH at equilibrium, to go with this statement you made earlier?

"Indoor air with a CO2 level of 700 ppm will lower the pH of seawater equilibrated with it by about 0.3 pH units compared to aeration with 350 ppm CO2 outside air."

The relationship is fairly simple, even though it looks like a messy mathematical equation. For water perfectly equilibrated with the air, the concentration of CO2 and carbonic acid in the water is directly related to the CO2 level in the air. Double the CO2 in the air, CO2 and carbonic acid in the water doubles. That also means the H+ approximately doubles.

Since pH is logarithmic, a doubling of H+ means a drop of about 0.30 in pH units.

So doubling of CO2 means a drop of about 0.3 pH units at equilibrium.

Going from 400 to 1200 ppm CO2 would cause a ph drop of about 0.48 pH units, or pH 8.20 to pH 7.72.