TRYING TO RAISE pH BY REDUCING CO2 FROM CALCIUM REACTOR

[Randy Holmes-Farley Verified Community Expert]

It is unused co2 that escapes the reactor that is the problem, not the pH of the effluent.

I agree that "unused CO2" is an issue that can be adjusted to not have it (that is, minimize CO2 addition for a given alk added), but all of the CO2 added by the tank does help depress tank pH.

The reactor does this:

CaCO3 + H20 + CO2 --> 2 HCO3- + Ca++

which sounds like there is no CO2 being added, but it's a mirage, because when the bicarbonate is used, all of that same CO2 is released again:

2HCO3- + Ca++ --> CaCO3 (coral skeleton) + H2O + CO2

Same effect as if one adds alk as bicarbonate directly (baking soda).

 

[Dr. Jim]

It is unused co2 that escapes the reactor that is the problem, not the pH of the effluent. This is nearly impossible to measure and hardest for most people to understand. People look at media and all of that, but it does not matter. If the airborne co2 is in the 400s or 500s, then your reactor is letting unused co2 in the tank if it is the reason that your tank pH is low. If this is true, then it is the design. In the most simple terms the easier the reactor, the worse the design for efficiency... if you want a reactor that is efficient, then you have to tune it yourself to balance co2 with contact time (flow and time). That area in the Deltec with the co2 bubble has to be as large as possible to accommodate a very high load, which means that it is likely too large under normal loads and more gas exchange is happening than needed (and escaping)... easy to work, but not efficient. IMO, for a reactor like the deltec to be efficient, the surface area of the co2 bubble would need to be shrunk or enlarged to balance contact with time and flow for the desired output. Cannot have unlimited access to co2 - same with having too much co2 in the air, the greedy water will gobble up too much. This is similar to having a carburetor with the maximum fuel (or air) and you only regulated the other - it would run, but would likely run be nowhere near efficient since you need to regulate access to both in a good ratio.

38 dKh is not a problem in it's self - plenty reasonable. I could tune my Korallin to be at 38 but not have excess co2 go into the tank. I could also tune it to where all kinds of co2 left the reactor with a dKh of 38 with too much co2 and too much flow... like letting a carbonated water into the tank (this is not exactly true, but you get it).

Early I said that maybe the Reborn will dissolve faster than the hard Deltec calcite. But, would you say it is true that the speed or ease of media dissolving isn't important but rather the level of dKh in the effluent? Assume that we are talking about the Deltec where the only thing that can be controlled is the effluent volume per day.
I'm thinking that whatever media yields the highest dKh, the less effluent I will need and in turn, the less CO2 will enter the tank. Does this sound accurate? If so, than even if the Reborn dissolves faster, if it doesn't produce a higher dKh then there is no advantage of using it instead of the Deltec calcite I'm presently using. Correct?

 

[Dr. Jim]

I agree that "unused CO2" is an issue that can be adjusted to not have it (that is, minimize CO2 addition for a given alk added), but all of the CO2 added by the tank does help depress tank pH.

The reactor does this:

CaCO3 + H20 + CO2 --> 2 HCO3- + Ca++

which sounds like there is no CO2 being added, but it's a mirage, because when the bicarbonate is used, all of that same CO2 is released again:

2HCO3- + Ca++ --> CaCO3 (coral skeleton) + H2O + CO2

Same effect as if one adds alk as bicarbonate directly (baking soda).

So if the Deltec CaRx draws more CO2 into it than needed and therefore releases it in the effluent, is it true that the only way to reduce excess CO2 would be by finding a media that produces the highest dKh which in turn would allow a lower amount of effluent per day? (Again, there are no adjustments on the Deltec to reduce the CO2 intake).

 

[jda]

I agree that "unused CO2" is an issue that can be adjusted to not have it (that is, minimize CO2 addition for a given alk added), but all of the CO2 added by the tank does help depress tank pH.

The reactor does this:

CaCO3 + H20 + CO2 --> 2 HCO3- + Ca++

which sounds like there is no CO2 being added, but it's a mirage, because when the bicarbonate is used, all of that same CO2 is released again:

2HCO3- + Ca++ --> CaCO3 (coral skeleton) + H2O + CO2

Same effect as if one adds alk as bicarbonate directly (baking soda).

I am not a chemist to do formulas, but a badly tuned CaRx does this

CaCO3 + H20 + CO2 --> 2 HCO3- + Ca++

plus this, as inefficiency:

If the tank can take away the seltzer water part, then the rest of it does not seem to impact the tank pH much at at all in my experience... like less than .05 pH in my decades of using one. Some of this might be that the release co2 is in close proximity to where phytosynthesis is happening, or whatever... again, I have never cared too much since it did not matter once I figured out how to tune a reactor. I have helped to tune reactors where the finished product used like 1/5th, or more, of the co2 that it did before, so the seltzer water inefficiency can be quite large, IME.

What would happen if you added in more co2 to the first part of the formula? I dunno.

(CaCO3 + H20 + CO2) + CO2
^ the CaRx part..............^the inefficient seltzer water part

It seems similar to a combustion engine equation, but then add in straight fuel along with it if an engine runs rich that just get passed along. Too bad there is not a catalytic converter for a calcium reactor.

Most people don't get the extra co2 part, which is the biggest thing, IMO, because they cannot measure it nor does it get added into a formula. They think that if they have some "automatic" thing "controlling" their CaRx that it is efficient, but pH probes and meters are a sine wave of dump-and-wait and co2 pooling (like the Deltec here) have too much co2 available at all times. The ease takes away from the efficiency.

 

[jda]

So if the Deltec CaRx draws more CO2 into it than needed and therefore releases it in the effluent, is it true that the only way to reduce excess CO2 would be by finding a media that produces the highest dKh which in turn would allow a lower amount of effluent per day? (Again, there are no adjustments on the Deltec to reduce the CO2 intake).

Even if you could find some that works with your co2 surface area and contact time (output), your next bag would likely not be the same or would change if you had to raise/lower the output. With an efficient tune, I have had to adjust from bag to bag with natural media - the same reborn, for example, did not dissolve as well as the larger stuff did. The same with ARM over the years. I don't know how you could ever do this.

The media that requires more co2 also would need more reaction time which then again would allow more co2 from the reactor bubble into the mixture, and you would be right back where you started.

The only way to correct this, IMO, is to limit the co2 which is not possible on the Deltec which is why it is inefficient.

 

[Dr. Jim]

This is very discouraging for a Deltec owner. But the question now is why is @steveweast getting by with 14 L/day (with his larger tank and probably greater alk demand) while I need 90 L/day. The only difference between our reactors is the media. At this point, I still think I need to try the Reborn. If that doesn't help, anybody want to buy a used Deltec for cheap? :)

 

[jda]

So if the Deltec CaRx draws more CO2 into it than needed and therefore releases it in the effluent, is it true that the only way to reduce excess CO2 would be by finding a media that produces the highest dKh which in turn would allow a lower amount of effluent per day? (Again, there are no adjustments on the Deltec to reduce the CO2 intake).

I don't think that any of this matters since you always have the possibility of too much raw co2 since you cannot limit it the gas. The only to make the deltec efficient would be just to luckily get a balance of media melt with demand (time and flow), which I doubt is possible or else the reactor would not be good for high-demand tanks (you would have to max it out).

Again, back to the carburetor analogy if you could only control air or fuel, you might be efficient at exactly 4200 RPM, but anything above or below this would be too rich or too lean. In the Deltec's case, the air bubble in the reactor is likely sized to never be too little (or else it would be size limited too small for large tanks), so you are always running co2 rich.

I do think that easier to melt media might produce more output with less liters, but you still would likely have excess co2 entering the tank. Natural media is likely a solid choice, but for a different reason that raising tank pH, which is an entirely different part of my made-up equation above with the seltzer water addition to the CaRx equation.

 

[Randy Holmes-Farley Verified Community Expert]

Early I said that maybe the Reborn will dissolve faster than the hard Deltec calcite. But, would you say it is true that the speed or ease of media dissolving isn't important but rather the level of dKh in the effluent? Assume that we are talking about the Deltec where the only thing that can be controlled is the effluent volume per day.
I'm thinking that whatever media yields the highest dKh, the less effluent I will need and in turn, the less CO2 will enter the tank. Does this sound accurate? If so, than even if the Reborn dissolves faster, if it doesn't produce a higher dKh then there is no advantage of using it instead of the Deltec calcite I'm presently using. Correct?

Aragonite will dissolve with a bit less CO2 than will calcite.

 

[Randy Holmes-Farley Verified Community Expert]

I am not a chemist to do formulas, but a badly tuned CaRx does this

CaCO3 + H20 + CO2 --> 2 HCO3- + Ca++

plus this, as inefficiency:

If the tank can take away the seltzer water part, then the rest of it does not seem to impact the tank pH much at at all in my experience... like less than .05 pH in my decades of using one. Some of this might be that the release co2 is in close proximity to where phytosynthesis is happening, or whatever... again, I have never cared too much since it did not matter once I figured out how to tune a reactor. I have helped to tune reactors where the finished product used like 1/5th, or more, of the co2 that it did before, so the seltzer water inefficiency can be quite large, IME.

What would happen if you added in more co2 to the first part of the formula? I dunno.

(CaCO3 + H20 + CO2) + CO2
^ the CaRx part..............^the inefficient seltzer water part

It seems similar to a combustion engine equation, but then add in straight fuel along with it if an engine runs rich that just get passed along. Too bad there is not a catalytic converter for a calcium reactor.

Most people don't get the extra co2 part, which is the biggest thing, IMO, because they cannot measure it nor does it get added into a formula. They think that if they have some "automatic" thing "controlling" their CaRx that it is efficient, but pH probes and meters are a sine wave of dump-and-wait and co2 pooling (like the Deltec here) have too much co2 available at all times. The ease takes away from the efficiency.

I certainly agree that a less than optimal tuning, allowing in more CO2 than needed, will depress pH more than necessary.