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Got Into a Debate

Unexpected

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The TL/DR version of the conversation is that my tank can not be 0dKH as nitrification stops without a carbonate source. Here's the article he sites for the claim. How Alkalinity Affects Nitrification | California Water Environment Association

It indeed states nitrification stops when carbonates are depleted.

His arguments, RO system and testing methods are not accurate enough or the equipment does not produce 0TDS water. The addition of fertilizer, where no carbonates are being added, the food given to the tank are the sources of carbonates/bicarbonates. Additionally, snails and shrimp are a source of carbonates and enough to maintain nitrification.

Initially, I thought he was going on about needing KH to keep a higher pH for nitrification and as such linked @Dennis Wong link Nitrification in a Biofilm at Low pH Values: Role of In Situ Microenvironments and Acid Tolerance

In this experiment, they do add carbonates to the reactor system.

So, are our tanks not truly 0dKH?
 
The TL/DR version of the conversation is that my tank can not be 0dKH as nitrification stops without a carbonate source. Here's the article he sites for the claim. How Alkalinity Affects Nitrification | California Water Environment Association

It indeed states nitrification stops when carbonates are depleted.

His arguments, RO system and testing methods are not accurate enough or the equipment does not produce 0TDS water. The addition of fertilizer, where no carbonates are being added, the food given to the tank are the sources of carbonates/bicarbonates. Additionally, snails and shrimp are a source of carbonates and enough to maintain nitrification.

Initially, I thought he was going on about needing KH to keep a higher pH for nitrification and as such linked @Dennis Wong link Nitrification in a Biofilm at Low pH Values: Role of In Situ Microenvironments and Acid Tolerance

In this experiment, they do add carbonates to the reactor system.

So, are our tanks not truly 0dKH?
Our tanks are not truly 0dKH, no. All aquariums have some alkalinity. Most people only have drop tests, which aren’t precise enough to measure really between 0-1. I have a Hanna alkalinity colorimeter, so I can test my alkalinity to the ppm. I use RO and add no alkalinity and my tank measures between 0.5 and 1 on average.
 
Our tanks are not truly 0dKH, no. All aquariums have some alkalinity. Most people only have drop tests, which aren’t precise enough to measure really between 0-1. I have a Hanna alkalinity colorimeter, so I can test my alkalinity to the ppm. I use RO and add no alkalinity and my tank measures between 0.5 and 1 on average.
Where does the alkalinity come from?
 
Water always has alkalinity. Even when acidic it’s not testable via the methods and the way we refer to alkalinity. Water is H2O. It dissociates into H+ and OH- and stays in equilibrium.

The OH- is alkalinity. Carbonate alkalinity is another one that exists if you have carbon in water as CO3(-2). Sorry for the formatting I don’t know how to subscripts and super scripts on my phone. Carbonate alkalinity also dissociates in water. Below is copied from Wikipedia on carbonates.
  1. H+ + HCO−3 ⇌ H2CO3
  2. H2CO3 ⇌ CO2(aq) + H2O
  3. CO2(aq) ⇌ CO2(g)
So we do have alkalinity it just is not testable using the typical pH indicator methods because of the acid base equilibrium i mentioned above and the form the alkalinity is in. (I prefer the word alkalinity just because my career requires differentiation between carbonates, bicarbonates, and alkalinity - for us alkalinity covers everything we need to focus on).

I’m sure someone can get more in-depth than my Fischer Price explanation above (I think that is the jist of it). I can dig more into when I’m finished getting tires on my truck LOL. Thank you for the distraction!! It’s been a long week…
 
Water always has alkalinity. Even when acidic it’s not testable via the methods and the way we refer to alkalinity. Water is H2O. It dissociates into H+ and OH- and stays in equilibrium.

The OH- is alkalinity. Carbonate alkalinity is another one that exists if you have carbon in water as CO3(-2). Sorry for the formatting I don’t know how to subscripts and super scripts on my phone. Carbonate alkalinity also dissociates in water. Below is copied from Wikipedia on carbonates.
  1. H+ + HCO−3 ⇌ H2CO3
  2. H2CO3 ⇌ CO2(aq) + H2O
  3. CO2(aq) ⇌ CO2(g)
So we do have alkalinity it just is not testable using the typical pH indicator methods because of the acid base equilibrium i mentioned above and the form the alkalinity is in. (I prefer the word alkalinity just because my career requires differentiation between carbonates, bicarbonates, and alkalinity - for us alkalinity covers everything we need to focus on).

I’m sure someone can get more in-depth than my Fischer Price explanation above (I think that is the jist of it). I can dig more into when I’m finished getting tires on my truck LOL. Thank you for the distraction!! It’s been a long week…
Thank you. Forgive my lack of education here. But I gather from above, water interaction with air allows for carbonate alkalinity? I guess this is just the “nature” of water?
 
Thank you. Forgive my lack of education here. But I gather from above, water interaction with air allows for carbonate alkalinity? I guess this is just the “nature” of water?

The air you breathe is mostly nitrogen and oxygen....there's some CO2 in it, too. All will enter your tank's water column until they're in equilibrium. The CO2 that enters will undergo the carbonate buffering reactions described above and, yes, some carbonates will form as a result

So, yeah, its a bit of a misnomer to say our tanks are at 0 dKH....instead, I think of 0 dKH as meaning my RO source water is at 0 dKH and I don't reconstitute it with any source of carbonates (baking soda, K2CO3, etc) after a water change
 
The air you breathe is mostly nitrogen and oxygen....there's some CO2 in it, too. All will enter your tank's water column until they're in equilibrium. The CO2 that enters will undergo the carbonate buffering reactions described above and, yes, some carbonates will form as a result

So, yeah, its a bit of a misnomer to say our tanks are at 0 dKH....instead, I think of 0 dKH as meaning my RO source water is at 0 dKH and I don't reconstitute it with any source of carbonates (baking soda, K2CO3, etc) after a water change
Thank you very much.
 
Where does the alkalinity come from?
To add on more to what’s already been said-

I’m going to post these two Barr Report articles related to carbon in our aquariums:
What these articles tell us:
  • An aquarium becomes an aquatic ecosystem which, like Earth's ecosystems, experiences the carbon cycle (cue vague middle school science memories.)
  • The cycling of carbon involves transition between organic and inorganic states.
    • 661E5F7B-8AB3-4953-A479-DAC358799736.jpeg
  • These transitions are influenced by, and themselves influence, a number of physico-chemical factors such as light, tem- perature, dissolved oxygen, pH, redox potential, ionic composition of the water, as well as biological factors such as productivity.
  • Alkalinity (also carbonate alkalinity, alkaline reserve, titratable base, or acid-binding capacity) has little to do with how alkaline water is. Rather, it refers to the quantity and kinds of compounds present in natural waters that act as buffers.
  • Another way to consider alkalinity is as the acid neutralizing capacity (ANC), which refers to the capacity to neutralize strong acids such as HCI,
    H2SO4, and HNO;. In other words, alkalinity is the ability of an aquatic system to accept protons (H).
  • Table 4 discusses several other components that influence alkalinity besides bicarbonates and carbonates:
    • D573E282-B7F9-4B10-8FA8-942102E09350.jpeg
  • Here is the Bjerrum plot, which describes the makeup of DIC at different PHs:
    • E693D0CB-5ED9-48F4-9DC0-70188014142A.png
    • Thus, in most planted aquariums, carbonate is not a large portion of inorganic carbon. Carbonate is much more present in more alkaline tanks/waters like African Cichlid tanks and Saltwater aquariums/the ocean.
 
Last edited:
To add on more to what’s already been said-

I’m going to post these two Barr Report articles related to carbon in our aquariums:
What these articles tell us:
  • An aquarium becomes an aquatic ecosystem which, like Earth's ecosystems, experiences the carbon cycle (cue vague middle school science memories.)
  • The cycling of carbon involves transition between organic and inorganic states.
  • These transitions are influenced by, and themselves influence, a number of physico-chemical factors such as light, tem- perature, dissolved oxygen, pH, redox potential, ionic composition of the water, as well as biological factors such as productivity.
  • Alkalinity (also carbonate alkalinity, alkaline reserve, titratable base, or acid-binding capacity) has little to do with how alkaline water is. Rather, it refers to the quantity and kinds of compounds present in natural waters that act as buffers.
  • Another way to consider alkalinity is as the acid neutralizing capacity (ANC), which refers to the capacity to neutralize strong acids such as HCI,
    H2SO4, and HNO;. In other words, alkalinity is the ability of an aquatic system to accept protons (H).
  • Table 4 discusses several other components that influence alkalinity besides bicarbonates and carbonates:
  • Here is the Bjerrum plot, which describes the makeup of DIC at different PHs:
    • View attachment 3154
    • Thus, in most planted aquariums, carbonate is not a large portion of inorganic carbon. Carbonate is much more present in more alkaline tanks/waters like African Cichlid tanks and Saltwater aquariums/the ocean.
Thank you. Awesome write up.
 
Water always has alkalinity. Even when acidic it’s not testable via the methods and the way we refer to alkalinity. Water is H2O. It dissociates into H+ and OH- and stays in equilibrium.

The OH- is alkalinity. Carbonate alkalinity is another one that exists if you have carbon in water as CO3(-2). Sorry for the formatting I don’t know how to subscripts and super scripts on my phone. Carbonate alkalinity also dissociates in water. Below is copied from Wikipedia on carbonates.
  1. H+ + HCO−3 ⇌ H2CO3
  2. H2CO3 ⇌ CO2(aq) + H2O
  3. CO2(aq) ⇌ CO2(g)
So we do have alkalinity it just is not testable using the typical pH indicator methods because of the acid base equilibrium i mentioned above and the form the alkalinity is in. (I prefer the word alkalinity just because my career requires differentiation between carbonates, bicarbonates, and alkalinity - for us alkalinity covers everything we need to focus on).

I’m sure someone can get more in-depth than my Fischer Price explanation above (I think that is the jist of it). I can dig more into when I’m finished getting tires on my truck LOL. Thank you for the distraction!! It’s been a long week…
I came here to say I appreciate the Fischer Price explanation.
 
I came here to say I appreciate the Fischer Price explanation.
Thank you. Glad it made sense. The “Fischer price” reference was a self denigrating comment on my over simplified way of explaining. When I get technical, I end up using 10,000 words to say 8.
 
LOL Thanks for the chemistry discussion. A lot of this has always gone over my head. I was never good in the sciences.

For me, a few take aways:
  1. Always amazed at the depth of @plantbrain’s Barr Report newsletters from back in the day;
  2. Our hobby test kits are never that accurate; and
  3. Even with accurate test kits, our aquariums are living ecosystems that are constantly changing. Hence, a measurement is only valuable at the time taken and can quickly be outdated.
 
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