sodium bicarbonate vs Sodium carbonat(soda ash)

[mrtian97]

I have been using brs 2 parts with Randy's recipe for alk, ca and mg. I am using brs sodium bicarbonate for the alk. tank is doing very well, sps coral growing. My daily dose 180mL of soda ash mix and 95mL Calcium mix with using Kalk solutions for the ATO (8 tsp per 5 gallon). Alk steady at 7.5-8.4 , Ca at 440 and Mg 1,300 with 7mL per day.

Question: since I am about to run out my Sod Bicarbonate, should I try Soda Ash? Just curious if using Soda Ash will reduce my daily dose for Alk from 180mL to 90mL? I read somewhere that Soda Ash mix is more concentrated than Sod Bicarb

Thanks

 

[Randy Holmes-Farley]

One can (but don't need to) make the sodium carbonate solutions more concentrated because it is more soluble than sodium bicarbonate.

The only difference between the two is that the carbonate doses will boost pH while the bicarbonate will not. Which to pick depends on your circumstances. Most people use the carbonate because their pH tends to run low.

 

[bdare]

I've had problems with soda ash. Caused precipitation in my tank. I would stick with the baking soda.

 

[mrtian97]

Thanks, if I switch to Soda Ash, do I. need to flush my auto dosing line from the sodium bicarbonate line before making the switch?

How much pH would soda ash increases? my pH stable between 8 - 8.2.
The reason I like to try because following BRS 2 parts recipe, the volume of soda ash solution is 50% less than the sod bicarbonate solution. This helps me as my dosing container is only 1,000 mL, so I only need to dose 90mL per day which match with my Ca daily dosing and last me 1 wk without having to refill midweek

 

[Fish Keeper82]

I made the switch for the same reason you did. Its been great not refilling the continers as often. I have no precipitation residue on my powerheads or pumps. I was surprised not to have any as I expected a little bit.
As far a PH rise goes, as long as the doses are small I see no noticable rise and im dosing 99 ml a day(11 doses of 9ml). Be sure not to make a mistake and dose too much Soda Ash solution at once though as you will get a dangerous PH spike. I still use Sodium Bicarbonate solution for any larger adjustments after testing so as not to have a PH spike.

 

[Randy Holmes-Farley]

Thanks, if I switch to Soda Ash, do I. need to flush my auto dosing line from the sodium bicarbonate line before making the switch?

How much pH would soda ash increases? my pH stable between 8 - 8.2.
The reason I like to try because following BRS 2 parts recipe, the volume of soda ash solution is 50% less than the sod bicarbonate solution. This helps me as my dosing container is only 1,000 mL, so I only need to dose 90mL per day which match with my Ca daily dosing and last me 1 wk without having to refill midweek

No on the flush.

Washing soda (carbonate) instantly boosts pH by about 0.35 pH units for each 1.4 dKH of alk added. The effect is much smaller when added slowly.

 

[mrtian97]

Thanks Randy

 

[Randy Holmes-Farley]

You're welcome.

Happy Reefing.

 

[CherBear811]

So, soda increases pH. Bicarb doesnt affect pH and would be best if pH is already stable?

 

[CherBear811]

Randy, on the +.35 pH per 1.4 dkh added..... is that per gallon? I mean... surely if you added 1 dkh to 100 gallons, it would not raise pH to the total volume as it would a 10 gallon tank? So, is that 1.4 dkh per gallon?

 

[mcarroll]

If you're running a dosing pump where only tiny amounts are added throughout the day, I suspect the effect on pH is negligible. I like the sodium bicarbonate option for the reasons @bdare mentioned and more.

 

[chipmunkofdoom2]

@CherBear811 most of the carbonate exists as bicarbonate in seawater. Only a small portion exists as carbonate. When you dose carbonate, the carbonate "wants" to become bicarbonate to maintain this natural balance. Stating that carbonate "wants" to be bicarbonate glosses over all of the intricacies of how seawater is buffered, but it gives you the general idea of what's going on. So, carbonate joins up with water and CO2 to become bicarbonate. This is why sodium carbonate (soda ash) raises pH: it uses CO2 from the water. Decreasing CO2 concentration raises pH in seawater, which is why opening a window or CO2 scrubbers work.

When you dose sodium bicarbonate, since most of the carbonate exists as bicarbonate in seawater, not much happens. A few of the bicarbonate will "want" to become carbonate to keep equilibrium between the different carbonate species, so a few of them will transition from bicarbonate to carbonate. The process is the same as carbonate to bicarbonate, but in reverse. CO2, water and carbonate are produced, which actually lowers the pH very slightly. Because almost all of the bicarbonate will remain bicarbonate, however, the pH drop is very small (0.04 pH units per 1.4 dKh increase).

And Randy can clarify, but no, the pH increase is overall, not per gallon. In a 1 gallon tank, to take carbonate alkalinity from 7.0 dKh to 8.4 dKh (a 1.4 dKh increase) you only need 1 mL of soda ash supplement. To raise a 100 gallon aquarium from 7 dKh to 8.4 dKh (a 1.4 dKh increase) you need 100 mL of soda ash supplement. This is why the pH increase is overall, not per gallon. The reason it is an overall increase to pH is partially because of the amount of supplement you need to dose, especially for larger tanks, but also due in part to how sodium carbonate behaves in seawater (see above).

 

[Randy Holmes-Farley]

So, soda increases pH. Bicarb doesnt affect pH and would be best if pH is already stable?

I actually think that most people benefit from a pH boost, unless they also use limewater.

I’m not sure what you mean by stable. pH stability is a different issue than whether it is high or low.[emoji3]

 

[Randy Holmes-Farley]

Randy, on the +.35 pH per 1.4 dkh added..... is that per gallon? I mean... surely if you added 1 dkh to 100 gallons, it would not raise pH to the total volume as it would a 10 gallon tank? So, is that 1.4 dkh per gallon?

dKH is already in units of alkalinity per unit volume. It would not make sense to say dKH per gallon.

 

[CherBear811]

Randy, stable probably wasn't the best word. I use kalk and it keeps my pH where I want it. Since I'm not looking to increase pH, would soda be the best choice?

And after looking at your recipes again.... does baking baking soda convert it to soda carb?

Finally, by saying dkh is already in a volume unit, what is the volume? If I add 10 ml of solution containing 1.4 dkh, is that ppm? 1.4 dkh per 10 ml in a tank will dilute to a tiny fraction of that, right? I know I'm going to feel extremely stupid once this clicks. Lol

 

[CherBear811]

@CherBear811 most of the carbonate exists as bicarbonate in seawater. Only a small portion exists as carbonate. When you dose carbonate, the carbonate "wants" to become bicarbonate to maintain this natural balance. Stating that carbonate "wants" to be bicarbonate glosses over all of the intricacies of how seawater is buffered, but it gives you the general idea of what's going on. So, carbonate joins up with water and CO2 to become bicarbonate. This is why sodium carbonate (soda ash) raises pH: it uses CO2 from the water. Decreasing CO2 concentration raises pH in seawater, which is why opening a window or CO2 scrubbers work.

When you dose sodium bicarbonate, since most of the carbonate exists as bicarbonate in seawater, not much happens. A few of the bicarbonate will "want" to become carbonate to keep equilibrium between the different carbonate species, so a few of them will transition from bicarbonate to carbonate. The process is the same as carbonate to bicarbonate, but in reverse. CO2, water and carbonate are produced, which actually lowers the pH very slightly. Because almost all of the bicarbonate will remain bicarbonate, however, the pH drop is very small (0.04 pH units per 1.4 dKh increase).

And Randy can clarify, but no, the pH increase is overall, not per gallon. In a 1 gallon tank, to take carbonate alkalinity from 7.0 dKh to 8.4 dKh (a 1.4 dKh increase) you only need 1 mL of soda ash supplement. To raise a 100 gallon aquarium from 7 dKh to 8.4 dKh (a 1.4 dKh increase) you need 100 mL of soda ash supplement. This is why the pH increase is overall, not per gallon. The reason it is an overall increase to pH is partially because of the amount of supplement you need to dose, especially for larger tanks, but also due in part to how sodium carbonate behaves in seawater (see above).

Thank you so much Chipmunk! I get it now. That makes perfect sense.

 

[Randy Holmes-Farley]

Randy, stable probably wasn't the best word. I use kalk and it keeps my pH where I want it. Since I'm not looking to increase pH, would soda be the best choice?

And after looking at your recipes again.... does baking baking soda convert it to soda carb?

Finally, by saying dkh is already in a volume unit, what is the volume? If I add 10 ml of solution containing 1.4 dkh, is that ppm? 1.4 dkh per 10 ml in a tank will dilute to a tiny fraction of that, right? I know I'm going to feel extremely stupid once this clicks. Lol

It a complicated issue.

Carbonate is what is consumed in coral calcification. Dosing it seems to have a net pH boost, but in reality it doesn’t because there’s a slower pH lowering effect when corals consume it.

If you dose bicarbonate, it has a very tiny pH lowering effect when added, and a slower pH lowering effect later when calcification takes place.

Unless pH is already too high, I’d use carbonate (or hydroxide if you want a bigger boost), but it is easy to try both bicarbonate and carbonate and see which your prefer (or even mix them if you are a true perfectionist).

 

[DiZASTiX]

Does the effect of the pH increase persist, or must we dose sodium carbonate consistently over time?

Never mind. I see what @Randy Holmes-Farley wrote about it being an effect that will even out to 0 no matter carbonate or bicarbonate, over time.

 

[mcarroll]

While there is no net effect on pH, in the short term I would think that rapidly photosynthesizing corals could potentially benefit from the increase in CO2 delivered by bicarbonate dosing.

I certainly benefit by not having to bake my baking soda.

 

[Esquire805]

Ok so how much washing powder is safe to dose. Is it 1 mil per gallon