Carbon Capture in Reef Aquariums

Treefer32

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I've talked about and had a lot of conversations around the impacts of dosing Carbon (C) to reef aquariums to fuel bacterial populations to consume nitrates. I have 4 mediums for consuming Nitrates in my tank, that generate bacterial populations that all consume Oxygen and increase Carbon Dioxide (CO2) within my 340 gallon mixed reef.

1. Algae turf Scrubber (consumes C and releases O2 into the water, not at the levels I need)
2. Vodka dosing, raising vodka dosing to 35 ml per day - Grows bacteria that consume O2 and release C into the water
3. Bio Pellet reactor - Breeds Nitrate reducing Bacteria that then consume O2 and releases C into the water
4. Matrix Rock along with Aqua Char - In a Cannister filter (filter cartridge removed and filled with matrix and Aqua Char) Bacterial populations should consume Nitrate, Oxygen and release Carbon.
5. Skimmer with CO2 reactor to filter CO2 from the air being injected into the water.

As a result of all this filtration I need Carbon Capture in my reef. My PH has dropped to 7.4 at night (calibrated Lab Grade PH probe in sump, near my skimmer output. During the day, it might get up to 7.7 - 7.75.

I at times wonder if there's a direct correlation or relationship to CO2, O2, and Nitrate Reducing bacteria levels. Is Bacteria O2 Limited. and what is the relationship between fresh O2 and PH?

My very limited understanding is that High O2 Levels = Higher PH. When I open the windows of my house, PH levels easily raise by .2-.3 during the day. I've not seen a PH of 8 since replacing and calibrating my PH probe. Which, leads me to believe I'm bordering near a crisis. If I had a power outage, how many minutes or hours am I from the fish suffocating to death without the pumps, circulation and skimmer of the tank operations? Obviously this can be off set by battery backup air pumps.

My goal is less about crisis management and more about how to have a healthy reef. Tank is 4 years operational going on it's 5th year.

I wanted to approach the question from a different direction. . . Is there an economical and easy to maintain way to capture carbon from my reef to enable greater oxygen saturation and increase the health of my reef's longevity. I don't know if it's suffering from old tank syndrome. Or If there's something I've done wrong over the years that has caused this situation. (Perpetual Nitrate production and the ever increasing need to perpetuate Nitrate eating bacteria).

I've looked at sulfur denitrators, but looking for something more economical and easier to maintain. Plus, between the four methods of nitrate reduction, something should work.
 

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My very limited understanding is that High O2 Levels = Higher PH. When I open the windows of my house, PH levels easily raise by .2-.3 during the day. I've not seen a PH of 8 since replacing and calibrating my PH probe. Which, leads me to believe I'm bordering near a crisis.

This is not correct. O2 has no effect on pH in seawater. It's CO2 and only CO2.

The reason bringing in outside air helps is because it's low in CO2. CO2 in Earth's atmosphere is around 400 ppm. The CO2 in well-sealed homes can be 1,000 ppm or above. When you lower the CO2 in the air surrounding your tank, your tank is able to offload excess CO2, which drives up the pH.

Randy's article on low pH is a good primer for understanding the relationship.
 
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Treefer32

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This is not correct. O2 has no effect on pH in seawater. It's CO2 and only CO2.

The reason bringing in outside air helps is because it's low in CO2. CO2 in Earth's atmosphere is around 400 ppm. The CO2 in well-sealed homes can be 1,000 ppm or above. When you lower the CO2 in the air surrounding your tank, your tank is able to offload excess CO2, which drives up the pH.

Randy's article on low pH is a good primer for understanding the relationship.
Thank you! And this actually reenforces my problem. Reading through the article I think I have two things going on.

1. My house is sealed quite well living in an extremely cold climate and only 6 years old. It's Sealed! I have 3 family members living in a 3000 square foot home. When all 3 of us are gone for 4 days or more. The PH of the tank raises within 2 days of us being gone. I assume reaching some form of equilibrium of air around the home. During the day it will easily hit close to 7.9 when no one is home.

2. However, I think the Nitrogen cycle is causing excessive CO2 to be disolved in my water (in a continual basis).

Root Cause analysis: I believe my root cause is my high nitrates. If my PH rises to 7.9 when no one is home with high bacterial populations injecting CO2 into the water. Then, I have to believe Lower bacterial populations would allow PH to hit 8.0 easily.


When I did not run any Denitrification tools other than the algae turf scrubber, which removed CO2. My PH would easily hit 8.3 at night and 8.5 during the day.


Now that I've been running Multiple mediums of Denitrification tools PH has remained below 7.8 in the daytime. So, back to my question, how do I remove CO2 from my water While, maintaining high denitrifying Bacterial populations. Or are the two mutually exclusive in the trade?


The circled pics in the image are the days no one was home. PH nearly hit 7.9, but not quite: You'll see on the 12th, before we left town, PH dipped to 7.54. Average PH is 7.69.

1674068205345.png
 

chipmunkofdoom2

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Low pH is very rarely due to the nitrogen cycle in a fully-cycled tank.

Try taking a cup of your tank water and aerating it with outside air for an hour. You can either take the air pump outside and run airline into the house, or you can take both the water and the air pump outside. After the hour is up, test the pH. If the pH is between 8.1 and 8.3, it's not the nitrogen cycle, it's 100% the CO2.
 

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I'm not sure I fully understand what we are trying to explain.

I am not aware of, and think it is unlikely that there is a strong decrease in nitrate uptake capacity at lower pH.

Most algae grow equal or better at lower pH due to more readily available CO2.

In the range we are talking about, bacteria will consume ethanol from vodka, and hence decrease nitrate by growing, fairly independent of pH.

The pH where true denitrification occurs (low O2 regions) will generally be low in pH for a variety of reasons, such as the conversion of the organics into CO2.


You may be correct that you will benefit from a CO2 scrubber to rasie pH. Many people use them.
 
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Treefer32

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Low pH is very rarely due to the nitrogen cycle in a fully-cycled tank.

Try taking a cup of your tank water and aerating it with outside air for an hour. You can either take the air pump outside and run airline into the house, or you can take both the water and the air pump outside. After the hour is up, test the pH. If the pH is between 8.1 and 8.3, it's not the nitrogen cycle, it's 100% the CO2.
I'm hoping you're right. I found a free fix if you are. I removed the CO2 scrubber. I had duct work for an air exchanger installed when the house was built. I haven't actually put the air exchanger in. However, the ducts from outside air and to the rest of the house are both there with zip ties sealing off the vents. I cut open the vent that had cold air inside of it (assuming it's outside air for it to be that cold) and ran the hose that was on the CO2 scrubber inside the air exchanger vent and then sealed it with a zip tie.

If it's truly needing purer outside air, then over the next 2-3 days I should see a sudden increase in PH. If it's not tied to cleaner air, then PH should remain the same as it has been. We will see. This should be no different than running the airline physically outside as the vent is duct hose is insulated and designed to bring outside air in for the air exchanger. I fed the hose up straight as far as I could go into the vent to get as close to outside as I could (About 6 -10 feet into the vent work).
 
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Treefer32

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I'm not sure I fully understand what we are trying to explain.

I am not aware of, and think it is unlikely that there is a strong decrease in nitrate uptake capacity at lower pH.

Most algae grow equal or better at lower pH due to more readily available CO2.

In the range we are talking about, bacteria will consume ethanol from vodka, and hence decrease nitrate by growing, fairly independent of pH.

The pH where true denitrification occurs (low O2 regions) will generally be low in pH for a variety of reasons, such as the conversion of the organics into CO2.


You may be correct that you will benefit from a CO2 scrubber to rasie pH. Many people use them.
Adding a CO2 Scrubber raised Average PH by .1.

My assumption and maybe it's a false assumption, was that Denitrifying bacteria consume O2? Which they self generated high CO2 zones in the ocean. However, I suppose the reverse could be true. They're only found in High CO2 Zones because that's what they like. It's not that they created the zone?
 

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I made a scrubber out of a copepod jar and attached it to my skimmer to help with CO2 capture. It does seem to raise my ph by about .2. I have to replace the sodalime every 2 weeks about.

I am growing chaeto in my sump to help absorb more of it. Its working, i can get up to 8.1 and the drop at night bottoms out at 7.9

We have a well sealed smaller house with me my wife 2 dogs a cat, bunch of freshwater tanks and 4 kids.

I have to dose phosphates to keep the chaeto from bottoming out my nutrients, but I'd rather dose phos and nitrates than struggle with ph below 7.9

I use 98% saturated kalkwasser in my ato, and switched my alk part of 2 part from bicarb to soda ash. This has made a big difference.

Prior to these measures, i had percipitation events when ph would drop to 7.5
 

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Have you considered reducing surface agitation on the display? Not sure how you have the flow set in your system although if the levels of co2 are actually higher inside the house, the surface agitation will be counterproductive as atmospheric co2 tends to find a equilibrium with water, reducing surface agitation should help if your air line is connected to the exterior of the property depending were you live, I would expect that if you live near a busy main road the circumstances may change :)
 

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Adding a CO2 Scrubber raised Average PH by .1.

My assumption and maybe it's a false assumption, was that Denitrifying bacteria consume O2? Which they self generated high CO2 zones in the ocean. However, I suppose the reverse could be true. They're only found in High CO2 Zones because that's what they like. It's not that they created the zone?

As the word is normally defined, denitrifying bacteria use nitrate in low O2 environments as an electron acceptor rather than O2 which normal aerobic organisms use.

In the absence of O2, and taking the nitrogen species completely to N2 (which may happen in several reaction steps), we have the following overall reaction:

organic + 124 NO3– + 124 H+ → 122 CO2 + 70 N2 + 208 H2O

It can be seen that the process above produces alkalinity (by consuming H+). In fact, it is the exact same amount of alkalinity that was depleted when the nitrate was originally formed from foods, so the net effect of the nitrogen cycle on alkalinity is zeroed out.



Bacteria that simply metabolize organics in an aerobic environment do consume O2.

In oxygen-containing environments, the reaction looks very similar to that shown above for plankton (ignoring phosphorus here):

organic + 175 O2 → 122 CO2 + 16 NO3– + 16 H+ + 138 H2O

where organic stands for a typical organic material ((CH2O)80(CH2)42(NH3)16) that is being metabolized.


 
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Treefer32

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Here I thought my low PH.
As the word is normally defined, denitrifying bacteria use nitrate in low O2 environments as an electron acceptor rather than O2 which normal aerobic organisms use.

In the absence of O2, and taking the nitrogen species completely to N2 (which may happen in several reaction steps), we have the following overall reaction:

organic + 124 NO3– + 124 H+ → 122 CO2 + 70 N2 + 208 H2O

It can be seen that the process above produces alkalinity (by consuming H+). In fact, it is the exact same amount of alkalinity that was depleted when the nitrate was originally formed from foods, so the net effect of the nitrogen cycle on alkalinity is zeroed out.



Bacteria that simply metabolize organics in an aerobic environment do consume O2.

In oxygen-containing environments, the reaction looks very similar to that shown above for plankton (ignoring phosphorus here):

organic + 175 O2 → 122 CO2 + 16 NO3– + 16 H+ + 138 H2O

where organic stands for a typical organic material ((CH2O)80(CH2)42(NH3)16) that is being metabolized.


Thank you, I didn't do well in Chemistry. So, don't fully understand the chemical equations. However, I did learn something from all the posts and conversations. More air that has less CO2 injected into the tank raises PH regardless of carbon dosing.

Over the last 2.5 hours, I've watched my PH of my entire 340 gallon tank raise from 7.70 (at 1:00 pm CST today) to 7.8. Which, it's not hit 7.8 unless we're all gone. It's continuing to rise, so I'm curious where it will end at. But so far using the air exchanger vent work as the air source seems to be having positive impacts.

I'm curious if it stabilizes or continues to rise over night. I've noticed my skimmer producing significantly more foam as well. Which I thought was odd it wasn't producing a ton of foam given the organic matter that must be in the tank. But maybe it needed more O2 to remove stuff as well? I don't know. I'll see where the needle goes over the next 2 days.
 
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Treefer32

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The third variable I'm trying to understand is Carbon Dosing. Whether it's through pellets, increased bacterial populations on things like matrix rock, Aqua Char, or through broadcast Vodka Dosing.

Why does Carbon Dosing (sugar, vodka, vinegar, etc) all lower PH? I feel like I'm fighting myself. Nitrates get too high (currently in the 60s despite my best efforts to increase vodka dosing), PH is low, increase vodka dosing, PH goes lower, and I'm in a vicious cycle. I'm tempted to stop dosing all vodka, let the PH rise and see if the problem takes care of itself, but I'm afraid my nitrates would go from 61 to 150 in the matter of a week or two.

Is there a way to have a safe PH level and dose high quantities of carbon to fuel bacteria?
 

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Why does Carbon Dosing (sugar, vodka, vinegar, etc) all lower PH?

Most or all of the carbon dosed ends up as CO2, potentially lowering pH. The pH effect is not that big for a small dose or a very well aerated tank, but is substantial in some situations.

I don't see the cycle you are mentioning. Low pH does not require or suggest more organic carbon is needed.

One can certainly dose organic carbon and have normal or even high pH. My pH ran 8.3 to 8.55 even with vinegar dosing.
 
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Treefer32

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Most or all of the carbon dosed ends up as CO2, potentially lowering pH. The pH effect is not that big for a small dose or a very well aerated tank, but is substantial in some situations.

I don't see the cycle you are mentioning. Low pH does not require or suggest more organic carbon is needed.

One can certainly dose organic carbon and have normal or even high pH. My pH ran 8.3 to 8.55 even with vinegar dosing.
Wow! O.k. Then I truly don't understand my PH issues. LOL. I guess not surprising. I asked my advanced chemistry teacher in high school (college level credit) to do more practical things in class than combining various chemicals to see what happens, and mentioned shouldn't we go out and measure PH and the different situations different PH's occur in nature. His response was - That's not chemistry, that's biology.

Little did he know that it's actually both. So, my confusion is that if dosing a carbon source increases CO2 levels, and evidently my home and surrounding air already has high levels of CO2 concentrations, could it not be inferred that dosing a carbon source will exasperate an existing problem? That problem being too high of CO2 concentrations?

My PH nearly hit 7.9 last night having moved the air line for my skimmer to a direct external air source. Behaviors of my fish changed. My Royal grammas that are normally in hiding in the rocks most of the day were out and active and playing with each other. My fish seemed to be more energetic than usual. I kinda wonder what effects the consistent PH below 7.6 was having on all of my livestock. If a significant behavior change could be noticed from 7.5 to 7.8 what health impacts were on fish and corals all this time?
 

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So, my confusion is that if dosing a carbon source increases CO2 levels, and evidently my home and surrounding air already has high levels of CO2 concentrations, could it not be inferred that dosing a carbon source will exasperate an existing problem? That problem being too high of CO2 concentrations?
If you want to dose organic Carbon for nutrient control and your indoor CO2 is too high, then it sounds like you have two options to elevate pH.
Increase aeration with an OUTSIDE air source (skimmer line pulling air in from outdoors).
The other way is to use higher pH boost additives for alkalinity.
https://www.reef2reef.com/threads/second-new-diy-two-part-recipe-with-higher-ph-boost.357080
But this method will be limited by your target alkalinity.
 

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Wow! O.k. Then I truly don't understand my PH issues. LOL. I guess not surprising. I asked my advanced chemistry teacher in high school (college level credit) to do more practical things in class than combining various chemicals to see what happens, and mentioned shouldn't we go out and measure PH and the different situations different PH's occur in nature. His response was - That's not chemistry, that's biology.

Little did he know that it's actually both. So, my confusion is that if dosing a carbon source increases CO2 levels, and evidently my home and surrounding air already has high levels of CO2 concentrations, could it not be inferred that dosing a carbon source will exasperate an existing problem? That problem being too high of CO2 concentrations?

My PH nearly hit 7.9 last night having moved the air line for my skimmer to a direct external air source. Behaviors of my fish changed. My Royal grammas that are normally in hiding in the rocks most of the day were out and active and playing with each other. My fish seemed to be more energetic than usual. I kinda wonder what effects the consistent PH below 7.6 was having on all of my livestock. If a significant behavior change could be noticed from 7.5 to 7.8 what health impacts were on fish and corals all this time?

If you pH is low like that and is not a measurement error, it is from you! Indoor elevated CO2.

Try this aeration test:



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.
 

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I have this same problem. I am a chemical engineer in Pensacola FL. I still don't fully understand this mechanism. Interestingly, my livestock (hammers included) do pretty well still around 7.6 pH. I am looking for a hob skimmer to help solve my problem, but i want to get a good brand. One thought I had is that...Should we consider the solubility of CO2 in atmospheric household conditions versus water? For example, if we say that if it's true that CO2 wants to be in the household air more, then it would always be beneficial to agitate the surface water more. If truly, generally, household atm has more CO2, then we'd want less surface agitation. Randy, I am a big fan fyi!! Second question, how did you get a good pH meter?? haha
 

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I have this same problem. I am a chemical engineer in Pensacola FL. I still don't fully understand this mechanism. Interestingly, my livestock (hammers included) do pretty well still around 7.6 pH. I am looking for a hob skimmer to help solve my problem, but i want to get a good brand. One thought I had is that...Should we consider the solubility of CO2 in atmospheric household conditions versus water? For example, if we say that if it's true that CO2 wants to be in the household air more, then it would always be beneficial to agitate the surface water more. If truly, generally, household atm has more CO2, then we'd want less surface agitation. Randy, I am a big fan fyi!! Second question, how did you get a good pH meter?? haha

Thanks!

Increased aeration in a home with elevated CO2 and a tank with normal CO2 (i.e., normal pH) will drive CO2 into the water and lower ph. CO2 in the air in contact with the water always wants to come to equilibrium in the water relative to the air.

Too many people make a blanket claim that surface agitation helps pH. It can lower it, raise it, or have no effect. That's why many folks want to aerate with outside air sent to a skimmer inlet.
 

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I have this same problem. I am a chemical engineer in Pensacola FL. I still don't fully understand this mechanism. Interestingly, my livestock (hammers included) do pretty well still around 7.6 pH. I am looking for a hob skimmer to help solve my problem, but i want to get a good brand. One thought I had is that...Should we consider the solubility of CO2 in atmospheric household conditions versus water? For example, if we say that if it's true that CO2 wants to be in the household air more, then it would always be beneficial to agitate the surface water more. If truly, generally, household atm has more CO2, then we'd want less surface agitation. Randy, I am a big fan fyi!! Second question, how did you get a good pH meter?? haha
Thanks!

Increased aeration in a home with elevated CO2 and a tank with normal CO2 (i.e., normal pH) will drive CO2 into the water and lower ph. CO2 in the air in contact with the water always wants to come to equilibrium in the water relative to the air.

Too many people make a blanket claim that surface agitation helps pH. It can lower it, raise it, or have no effect. That's why many folks want to aerate with outside air sent to a skimmer inlet.
Yeah, that's easy enough to understand. I assume that you have enough experience to say that the solubility equilibrium and carboxylic acid formation chemical equilibrium across "normal" ranges (normal for tank and normal for occupied house that is not often replenished with fresh air) always drives CO2 from air into water.
 

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Yeah, that's easy enough to understand. I assume that you have enough experience to say that the solubility equilibrium and carboxylic acid formation chemical equilibrium across "normal" ranges (normal for tank and normal for occupied house that is not often replenished with fresh air) always drives CO2 from air into water.

We have many users that have measured CO2 in their home air, along with lots of published studies, so we know how CO2 ranges, and we know pretty accurately what the pH of seawater is in equilibrium with those CO2 levels (some users run a program that computes it),.

In general, aeration both raises and lower pH, and may do both in the same tank at different times of the day.

In my tank, aeration lowered pH because pH always ran high (>8.3 with aeration by skimmer)) due to kalkwasser addition and significant photosynthesis, even at night in a reverse lit refugium.
 

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