Sodium Bisulfate to Reduce Alkalinity in New Salt Water or in Display Tanks

Randy Holmes-Farley

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I just want to record these calculations in their own thread to refer back to in other threads.

When alkalinity is too high in new salt water or in a display tank, acid can be used to lower the alkalinity. You can easily use muriatic acid (hydrochloric acid), or sodium bifulfate (e.g., Seachem Acid Buffer is this chemical, I think) or sulfuric acid (but that one is harder to get for hobbyists).

Note that these methods reduce pH a lot (and to the same extent), until you aerate adequately, so go very slow in a display and aerate a lot to drive off the excess CO2 that is generated.

Dropping alk by 1.4 dKH when starting at 6.3 dKH will drop pH below 7 (I got 6.9, experimentally). The effect is roughly linear with alkalinity, so starting at 12.6 dKH, a drop of 2.8 dKH will drop the pH to around 7 or a bit lower (depends on the starting pH, of course).

Sodium bisulfate is NaHSO4.

In seawater, it releases H+:

NaHSO4 ---> Na+ + H+ + SO4--

The H+ is what reduces the alkalinity, and the Na+ and SO4-- are not any concern:

H+ + CO3-- --> HCO3-

So, how much is needed?

NaHSO4 weighs 120.1 grams per mole. Thus, 120.1 grams has the potential to reduce alkalinity by 1 mole, or 1 equivalent, or 1000 meq (milliequivalents).

If you were to add that much to 1000 L, you would drop the alkalinity by 1000 meq/1000L = 1 meq/L = 2.8 dKH.

So 1.2 grams per 10 Liters, drops alkalinity by 2.8 dKH.

If you do not have a scale, we can roughly estimate how much is in a teaspoon:

1 cubic centimeter (1 mL dry) weighs roughly 1.44 grams.

A level teaspoon (4.93 mL) will then weigh roughly 7.1 grams.

1 level dry teaspoon of sodium bisulfate added per 100 L of tank water will drop the alkalinity by about 1.7 dKH.

Dissolve it in fresh water before adding it slowly to a high flow area.

DO NOT USE BISULFITE. Note the "i" in the ending vs an "a"

These materials should be fine to use:

https://www.amazon.com/Sodium-Bisulfate-Microprills-Ounces-Reagent/dp/B014AQ45DM/ref=sr_1_7?ie=UTF8&qid=1519584550&sr=8-7&keywords=sodium+bisulfate

https://www.amazon.com/Sodium-Bisulfate-Microprills-Ounces-Reagent/dp/B014AQ45DM/ref=sr_1_7?ie=UTF8&qid=1519584550&sr=8-7&keywords=sodium+bisulfate
 

marvelousone

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Thanks Randy. I started using Seachem Acid Buffer in my freash water before doing water change.
 

drawman

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I just want to record these calculations in their own thread to refer back to in other threads.

When alkalinity is too high in new salt water or in a display tank, acid can be used to lower the alkalinity. You can easily use muriatic acid (hydrochloric acid), or sodium bifulfate (e.g., Seachem Acid Buffer is this chemical, I think) or sulfuric acid (but that one is harder to get for hobbyists).

Note that these methods reduce pH a lot (and to the same extent), until you aerate adequately, so go very slow in a display and aerate a lot to drive off the excess CO2 that is generated.

Dropping alk by 1.4 dKH when starting at 6.3 dKH will drop pH below 7 (I got 6.9, experimentally). The effect is roughly linear with alkalinity, so starting at 12.6 dKH, a drop of 2.8 dKH will drop the pH to around 7 or a bit lower (depends on the starting pH, of course).

Sodium bisulfate is NaHSO4.

In seawater, it releases H+:

NaHSO4 ---> Na+ + H+ + SO4--

The H+ is what reduces the alkalinity, and the Na+ and SO4-- are not any concern:

H+ + CO3-- --> HCO3-

So, how much is needed?

NaHSO4 weighs 120.1 grams per mole. Thus, 120.1 grams has the potential to reduce alkalinity by 1 mole, or 1 equivalent, or 1000 meq (milliequivalents).

If you were to add that much to 1000 L, you would drop the alkalinity by 1000 meq/1000L = 1 meq/L = 2.8 dKH.

So 1.2 grams per 10 Liters, drops alkalinity by 2.8 dKH.

If you do not have a scale, we can roughly estimate how much is in a teaspoon:

1 cubic centimeter (1 mL dry) weighs roughly 1.44 grams.

A level teaspoon (4.93 mL) will then weigh roughly 7.1 grams.

1 level dry teaspoon of sodium bisulfate added per 100 L of tank water will drop the alkalinity by about 1.7 dKH.

Dissolve it in fresh water before adding it slowly to a high flow area.

DO NOT USE BISULFITE. Note the "i" in the ending vs an "a"

These materials should be fine to use:

https://www.amazon.com/Sodium-Bisulfate-Microprills-Ounces-Reagent/dp/B014AQ45DM/ref=sr_1_7?ie=UTF8&qid=1519584550&sr=8-7&keywords=sodium+bisulfate

https://www.amazon.com/Sodium-Bisulfate-Microprills-Ounces-Reagent/dp/B014AQ45DM/ref=sr_1_7?ie=UTF8&qid=1519584550&sr=8-7&keywords=sodium+bisulfate
@Randy Holmes-Farley I'm curious would you say that Sodium Bisulfate is less hazardous to work with than Muriatic acid for this application (ie fumes)? It seems like sodium bisulfate would be easier to store in an apartment so it may be my choice :D
 

marvelousone

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@Randy Holmes-Farley I'm curious would you say that Sodium Bisulfate is less hazardous to work with than Muriatic acid for this application (ie fumes)? It seems like sodium bisulfate would be easier to store in an apartment so it may be my choice :D
It is easire to keep and use.
 

Reefahholic

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Nice write up Randy! Thx!
 
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Randy Holmes-Farley

Randy Holmes-Farley

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Thank you for this. I like that I can get the sodium bisulfate in some sort of graded purity... I just don’t trust the muriatic acid from the hardware store.
That’s a good point. [emoji3]
 

VbReefer

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Been toying around with the idea of using muratic acid to being down alk of IO. I have some but it's the hardware store variety.
Given a choice I would definitely prefer a lab or food grade option. And the added safety is a plus.

Would any of you geniuses be kind enough to convert this into grams required to drop 1 gallon by 1 dKH? TIA
 

VbReefer

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Another reef forum buddy helped me with this. Thanks Adrian

He came up with .16g per gallon to drop 1dKH.
Also converted to ML at .113ml

I'll do 50gallons at a time so that's 8.17g
Or 5.65ml for 50 gallons down 1dkh

Anyone care to double check this before I record it as the gospel?
Just to double check the ML dosage is for dry product as well?correct?
 

Acorral

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Thanks Randy, great information !!!

So the same dosing applies to the seachem product? or only to the ones you are linking to?
 

chipmunkofdoom2

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Thanks Randy, great information !!!

So the same dosing applies to the seachem product? or only to the ones you are linking to?
From the sound of Randy's post, he is unsure if Seachem's product is sodium bisulfate. It's rather uncommon for manufacturers to be up-front about what kinds of chemicals they put in their supplements. If you are using the Seachem product, it's probably best to follow the exact directions on the product.
 

VbReefer

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From the sound of Randy's post, he is unsure if Seachem's product is sodium bisulfate. It's rather uncommon for manufacturers to be up-front about what kinds of chemicals they put in their supplements. If you are using the Seachem product, it's probably best to follow the exact directions on the product.
They only provide dosing information to drop pH and in FW I believe.
If anyone has a link to a thread where dosing for the seachem acid buffer is shown for this application please share.
 

KenO

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What about the sodium bisulfate that is sold for pools? Is that safe to use in aquariums?
 

chipmunkofdoom2

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What about the sodium bisulfate that is sold for pools? Is that safe to use in aquariums?
What @VbReefer said. It might be safe. But, it might not. Sodium bisulfate likely does not need to have low impurities to work in pools. There are, however, lots of elements that are problematic for reef tanks at very low levels. Impurities that might not be a problem for pools could be a big problem for reef aquaria. Food-grade products, on the other hand, must be sufficiently pure for human consumption. In general, stuff that is safe for humans appears to be safe to put in reef tanks.

Food-grade sodium bisulfate is really cheap, only $10 per bottle with free shipping from Etsy. Because you need so little to drop alkalinity by a relatively large amount, I don't think there's a compelling reason to use the stuff from the pool store over a food-grade additive.
 
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Randy Holmes-Farley

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@Randy Holmes-Farley do you have any recommendation of how much water to mix the solid into? Lets say I use a teaspoon of solid should I mix it in 100mL or so? I have mine on order from amazon :D
It won't matter how much you dissolve it in. It is very soluble. Max at room temp is close to 28 g/100 mL.
 
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Randy Holmes-Farley

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They only provide dosing information to drop pH and in FW I believe.
If anyone has a link to a thread where dosing for the seachem acid buffer is shown for this application please share.
While I would not suggest that you accept everything Seachem claims, and certainly not what others post to their web site, Seachem gives a value:

https://www.seachem.com/support/forums/forum/sunken-gardens/244-adding-seachem-acid-buffer-every-day

"Acid Buffer at a dose of 1/4 teaspoon per 20 gallons will lower your dKH by 0.6 points."
 
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