NOPOX & Alkalinity Reduction
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Defective_Weeble
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If we consider the mechanism of action of carbon dosing, when we increase the bacterial population in the tank we will be using more oxygen. Randy has a great article on that mechanism here - http://reefkeeping.com/joomla/index...ar-dosing-methodology-for-the-marine-aquarium
According to Red Sea "when dosing No3Po4-X you will see substantially more biological activity, cultures will be enlarging and developing as technically they are now being fed by the No3Po4-X, this in turn will increase the level of Co2 production via biological activity and you can see a small reduction in alkalinity, this stabilizes very quickly." - http://www.ultimatereef.net/forums/archive/index.php/t-711031.html
According to Red Sea "when dosing No3Po4-X you will see substantially more biological activity, cultures will be enlarging and developing as technically they are now being fed by the No3Po4-X, this in turn will increase the level of Co2 production via biological activity and you can see a small reduction in alkalinity, this stabilizes very quickly." - http://www.ultimatereef.net/forums/archive/index.php/t-711031.html
Randy Holmes-Farley
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My Tank Thread
Adding uncharged organic carbon molecules will have no net impact on alkalinity once they are fully metabolized to water and carbon dioxide. The added CO2 has no impact on alkalinity (and hopefully the Red Sea person commenting in the second link did not mean to imply that it did).
I show below that a normal dose of NOPOX should have only about a 0.01 dKH drop in alkalinity due to the issues relating to the acetic acid in it.
Anything else is not directly related to the NOPOX itself, and must be from corals growing faster (or similar effects), or may just be test error or coincidence. Folks often see no effect on alk when organic carbon dosing.
The following discussion details the rationale for the 0.01 dKH drop, which most won't care about...
NOPOX contains acetic acid and when it is added, one can get a lowering of alkalinity if you measure it after it is added to the tank but before it is metabolized. That alkalinity comes back as the acetate is metabolized.
The degree of this effect is pretty small. Most of the acetic acid added via NOPOX (or viengar) will still be counted but a small amount will not. And it is that small amount that leads to the small and temporary apparent decline in alkalinity. I show that with my own measurements titrating acetate in tank water here:
http://www.advancedaquarist.com/2002/2/chemistry
We can quantify the effect as follows.
NOPOX contains about 3% acetic acid.
The recommended dose is about 2 mL per 100 liters of tank water.
So that is 2 mL x 0.03 g/mL /100 L = 0.0006 grams of acetic acid per L or 0.01 meq/L.
Since only about 25% of this acetic ac id added appears in a drop in alkalinity (the rest being counted in an alk titration; see the link), the drop in alkalinity on giving a normal dose of NOPOX is less than 0.01 dKH.
I show below that a normal dose of NOPOX should have only about a 0.01 dKH drop in alkalinity due to the issues relating to the acetic acid in it.
Anything else is not directly related to the NOPOX itself, and must be from corals growing faster (or similar effects), or may just be test error or coincidence. Folks often see no effect on alk when organic carbon dosing.
The following discussion details the rationale for the 0.01 dKH drop, which most won't care about...
NOPOX contains acetic acid and when it is added, one can get a lowering of alkalinity if you measure it after it is added to the tank but before it is metabolized. That alkalinity comes back as the acetate is metabolized.
The degree of this effect is pretty small. Most of the acetic acid added via NOPOX (or viengar) will still be counted but a small amount will not. And it is that small amount that leads to the small and temporary apparent decline in alkalinity. I show that with my own measurements titrating acetate in tank water here:
http://www.advancedaquarist.com/2002/2/chemistry
We can quantify the effect as follows.
NOPOX contains about 3% acetic acid.
The recommended dose is about 2 mL per 100 liters of tank water.
So that is 2 mL x 0.03 g/mL /100 L = 0.0006 grams of acetic acid per L or 0.01 meq/L.
Since only about 25% of this acetic ac id added appears in a drop in alkalinity (the rest being counted in an alk titration; see the link), the drop in alkalinity on giving a normal dose of NOPOX is less than 0.01 dKH.
