Paul G
Active member
The carbonate is the only buffer ion in this system. Bearing in mind that the SWCR (Streaming Water Change Regimen) is constantly diluting the water column, it is necessary to provide a regular source of buffer in order to maintain the carbonate hardness. Carbonate ion pretty much supplies all the alkalinity needed to hold the preset. I prefer not to use the conventional bicarbonate alkalinity adjusters because they typically involve sodium, or do not state their exact composition at all. Sodium is an essential micronutrient, but, since buffer is dosed routinely I prefer that +Na is not kept at a concentration typical of secondary macronutrient. The great advantage of K2CO3 is that, like NaHCO3, it has very high water solubility, so is ideally suited to auto-dosing.
The usual source for potassium in 'bulk' quantity in most dosing schemes is K2SO4 (KNO3 is the usual source for nitrogen). Potassium concentrations are typically determined by adjustment of the K2SO4 dosing rate. Sulfur is a secondary macro and excess sulfate is biologically inert, not harmful as long as the environment is aerobic. Thus, sulfate can be a good way to dose potassium. But my preference is that +K be kept at concentrations guaranteeing luxury uptake availability, and that runs to 30 to 40 ppm +K. Potassium is completely non-toxic and surplus levels are not environmentally harmful. Also as a matter of personal preference, --SO4, while not uncommon in natural waters, is not high in primary streams - as a rule - and I would rather avoid it. However, established aquariums receiving regular fertilization with K2SO4 can have 100 ppm or more --SO4.
It makes sense, therefore, to dose K2CO3 as a means of providing macronutrient and alkalinity buffer in commensurate quantities, while relegating Na and S to their respective micro and secondary status. I am demonstrating here that the current dosing rate of K2CO3 solution is holding the carbonate hardness and the potassium at the desired levels exactly. This is working within the SWCR protocol as described in this journal. It is understandable that those practicing Estimative Index will have a completely different take on it.
The objective of the SWCR is to remove autochthonous product (waste evolved in the habitat) "downstream" by the ongoing process of replacing loaded water with pristine deionized water from "upstream" (no allochthonous nutrient input). The metric of this is maintenance of an oligotrophic characteristic which is defined as < 10 ppm DIN (dissolved inorganic nitrogen, mostly nitrate in aerobic environment), < 2 ppm orthophosphate, and diminishing DOM (dissolved organic matter, or DOC dissolved organic carbon) as indicated by high redox potential. At this point, feeding the fish and the general autochthonous generation of all product by environmental metabolism in a mature habitat is resulting in superoligotrophic status; < 5 ppm NO3, < 1 ppm PO4, and consistent minimum ORP of 500 mV. The plants consume N and P from these sources both by foliar uptake from the water column where these measurement are made, and in the rhizosphere of a mature substrate, which elude these measurements (but in which they certainly reside in abundance). Thus, I do not routinely dose with supplemental nitrate or phosphate. So there is no +K supplied by those means. I have a dosing vat containing a mixed KNO3 and KH2PO4 solution which is used sparingly on an ad hoc basis to hedge downward drift, but I very seldom do this adjustment because the plants show no malnutrition of any kind regardless of the measurements.
Another source of --CO3 is the hardness reconstitution reactor containing SeaChem Reef Reactor in a processing filter loop designed to support secondary nutrients ++Ca and ++Mg. I am routinely dosing MgSO4 in a small daily quantity to redress a Ca:Mg ratio imbalance and as secondary nutrient S, being the only main --SO4 source now used.
This system is automatically maintaining carbonate hardness at 5 - 7 dKH (exact value not critical but assures minimum 30 ppm CO2 at prevailing pH), and potassium pushing 40 ppm using K2CO3 solution in one doser on one schedule. Sulfate, nitrate, and phosphate salts play no role in this and can be independently controlled. Sodium remains a micro at appropriate concentration.
That is "why the potassium carbonate," but I must emphasize that the utility of this scheme is contextual with the SWCR. It is not advocated as an alternative method of supplementation in a different water management protocol wherein it would make no sense.
Thanks for the question. Always happy to have questions.
The usual source for potassium in 'bulk' quantity in most dosing schemes is K2SO4 (KNO3 is the usual source for nitrogen). Potassium concentrations are typically determined by adjustment of the K2SO4 dosing rate. Sulfur is a secondary macro and excess sulfate is biologically inert, not harmful as long as the environment is aerobic. Thus, sulfate can be a good way to dose potassium. But my preference is that +K be kept at concentrations guaranteeing luxury uptake availability, and that runs to 30 to 40 ppm +K. Potassium is completely non-toxic and surplus levels are not environmentally harmful. Also as a matter of personal preference, --SO4, while not uncommon in natural waters, is not high in primary streams - as a rule - and I would rather avoid it. However, established aquariums receiving regular fertilization with K2SO4 can have 100 ppm or more --SO4.
It makes sense, therefore, to dose K2CO3 as a means of providing macronutrient and alkalinity buffer in commensurate quantities, while relegating Na and S to their respective micro and secondary status. I am demonstrating here that the current dosing rate of K2CO3 solution is holding the carbonate hardness and the potassium at the desired levels exactly. This is working within the SWCR protocol as described in this journal. It is understandable that those practicing Estimative Index will have a completely different take on it.
The objective of the SWCR is to remove autochthonous product (waste evolved in the habitat) "downstream" by the ongoing process of replacing loaded water with pristine deionized water from "upstream" (no allochthonous nutrient input). The metric of this is maintenance of an oligotrophic characteristic which is defined as < 10 ppm DIN (dissolved inorganic nitrogen, mostly nitrate in aerobic environment), < 2 ppm orthophosphate, and diminishing DOM (dissolved organic matter, or DOC dissolved organic carbon) as indicated by high redox potential. At this point, feeding the fish and the general autochthonous generation of all product by environmental metabolism in a mature habitat is resulting in superoligotrophic status; < 5 ppm NO3, < 1 ppm PO4, and consistent minimum ORP of 500 mV. The plants consume N and P from these sources both by foliar uptake from the water column where these measurement are made, and in the rhizosphere of a mature substrate, which elude these measurements (but in which they certainly reside in abundance). Thus, I do not routinely dose with supplemental nitrate or phosphate. So there is no +K supplied by those means. I have a dosing vat containing a mixed KNO3 and KH2PO4 solution which is used sparingly on an ad hoc basis to hedge downward drift, but I very seldom do this adjustment because the plants show no malnutrition of any kind regardless of the measurements.
Another source of --CO3 is the hardness reconstitution reactor containing SeaChem Reef Reactor in a processing filter loop designed to support secondary nutrients ++Ca and ++Mg. I am routinely dosing MgSO4 in a small daily quantity to redress a Ca:Mg ratio imbalance and as secondary nutrient S, being the only main --SO4 source now used.
This system is automatically maintaining carbonate hardness at 5 - 7 dKH (exact value not critical but assures minimum 30 ppm CO2 at prevailing pH), and potassium pushing 40 ppm using K2CO3 solution in one doser on one schedule. Sulfate, nitrate, and phosphate salts play no role in this and can be independently controlled. Sodium remains a micro at appropriate concentration.
That is "why the potassium carbonate," but I must emphasize that the utility of this scheme is contextual with the SWCR. It is not advocated as an alternative method of supplementation in a different water management protocol wherein it would make no sense.
Thanks for the question. Always happy to have questions.
