Some results from sodium hydroxide dosing

[brooksdw]

May be calcium carbonate. As pH gets higher, the tendency to precipitate rises sharply.

Thats kind of what I was thinking .calcium levels were dropping .went from 400ppm to 285ppm over night .

 

[Randy Holmes-Farley Verified Community Expert]

Thats kind of what I was thinking .calcium levels were dropping .went from 400ppm to 285ppm over night .

Overnight?

That's test error unless you added a huge amount of sodium hydroxide. That would consume 16 dKH of alk to precipitate that much calcium.

 

[Iyad Aoun]

Are you serious dude?

A C02 scrubber works by blowing air over sodium hydroxide pellets and reducing C02 by some trivia amount. Then injecting that into your tank and hoping it displaces more saturated CO2 levels. Ive lost count how many complaints about people getting barely any results and blowing through pounds of sodium hydroxide pellets in a few weeks. Or having to result to looping it through skimmers.

Basically a CO2 scrubber is like taping a motrin to your forehead to solve a headache. Sodium hydroxide dosing is swallowing it.

My windows *are* wide open. I live in a metro area and my pH never gets higher than 8.15.

The amount of alk increase dry sodium hydroxide produces is about the same as sodium bicarb. Took awhile of digging to find Randy's comments on this. Seems to be about right. My tank consumes a bit less than a full teaspoon of sodium bicarb per day. So, the quantum mechanics here is 1 teaspoon minus 1/8 teaspoon ...might have to call a 3rd grader in on that.

Sorry to be short, but I just raised my tank pH significtly with a penny's worth of sodium hydroxide and got a big jump in alk consumption in 48 hours. Why in the world would you want to keep using a scrubber when you can raise pH for a fraction the price under more control ?

Hello
I am also using NaOh,I am using a serum montage with 20 drops per minute for a 200 gallons tank.Dissolving naoh in deionized water is stressing and dangerous but it"s worth it.My ph was always around 8,but now I have easily 8.4
On the other hand alcalinity is exploding with 12 as value.I always had 7 or 8 dkh,not to mention caco3 deposit on glasses and pumps,so more cleaning than ever ,but my corals are happy.Do you think that adding corals will lower somehow the kh since it will be consumed by more corals?
Thank you

 

[Randy Holmes-Farley Verified Community Expert]

Hello
I am also using NaOh,I am using a serum montage with 20 drops per minute for a 200 gallons tank.Dissolving naoh in deionized water is stressing and dangerous but it"s worth it.My ph was always around 8,but now I have easily 8.4
On the other hand alcalinity is exploding with 12 as value.I always had 7 or 8 dkh,not to mention caco3 deposit on glasses and pumps,so more cleaning than ever ,but my corals are happy.Do you think that adding corals will lower somehow the kh since it will be consumed by more corals?
Thank you

It seems you are adding too much, unless you are happy with 12 dKH as a target.. I recommend only adding enough to meet the alkalinity demand.

Adding hard corals will increase demand for alk and calcium.

 

[Gigajoulz]

Hydroxide has the highest pH raising effect of any possible alkalinity additive. It is part of my DIY ultra high pH two part systems:

https://www.reef2reef.com/threads/second-new-diy-two-part-recipe-with-higher-ph-boost.357080/
https://www.reef2reef.com/threads/new-diy-two-part-recipes-with-higher-ph-boost.344500/
When I tested hydroxide, adding 0.5 meq/l (1.4 dKH) of alk to raw instant ocean, it boosted pH instantly by 0.65 pH units. The rise is smaller when added slowly as CO2 is drawn in.

I think I am starting to realize that Hydroxide itself doesn't contain alk, but since its partly Alk it can be calculated given that eventually CO2 will be introduced to the tank to neutralize the Hydroxide and convert it to carb/bicarb. I've been dosing Red Sea Alk+ and have found that it raises the pH instantly as well as the dKH, but if I JUST wanted the pH to rise I would want to use NaOH right?

NaOH would crazy raise the pH, so I would use less of it to slightly raise the pH, and that would only slightly raise dKH overtime as CO2 is introduced, right...since that's not directly adding it like Soda Ash?

Before I started doing soda ash, my pH would swing daily between 7.6 and 7.9, but now its more stable and sits around 7.8 and 7.9. It sometimes rises on its own before I've added soda ash - but this is the part that is confusing me - why does the pH rise when I've not added anything? Please forgive me as I know I've been struggling to understand how Hydroxide > Carbonate > Bicarbonate or Soda Ash (Carbonate) > Bicarb effects the pH between those conversions.

 

[Gigajoulz]

NaOH would crazy raise the pH, so I would use less of it to slightly raise the pH, and that would only slightly raise dKH overtime as CO2 is introduced, right...since that's not directly adding it like Soda Ash?

err, I might have it backward - would using less to slightly raise pH, but give the potential to explode Alk later? given that I think CO2 is my problem (using a skimmer even.)

If Alk raises, I think that would cause a precipitation event if the pH also spiked (like if I didn't realize Alk was getting high and dosed again, raising pH in an already Alkaline tank).

 

[Randy Holmes-Farley Verified Community Expert]

Hydroxide directly and instantly adds alk detectable by testing. So there is no concern.

 

[Gigajoulz]

Hydroxide directly and instantly adds alk detectable by testing. So there is no concern.

does NaOH add alk directly and instantly because the hydroxide instantly pulls the CO2 out of the water, converting to carb and bicarb? if so, how is that unlike adding soda ash if either 1 gallon solution (soda ash or hydroxide) contains the same alkalinity of 5,300 dKH?

I used to top off with Kalkwasser, but I wasn't getting nearly the pH boost that I get from soda ash before hitting my evaporation point with Kalk. While dosing kalk, my alk seemed stable, but now that I'm dosing soda ash it seems to be all over the place, even though my pH is higher and more stable.

 

[Randy Holmes-Farley Verified Community Expert]

Hydroxide is counted in an alk test. It need not do anything to be counted.

In point of fact, it also almost instantly combines with bicarbonate to form carbonate, as well as some other things such as combining with CO2/carbonic acid. But none of those processes change alkalinity.

Hydroxide consumes a bit over twice as much CO2 as does carbonate as it is converted into bicarbonate, which is the main contributor to all in seawater.

I discuss these issues in great depth here:

https://reefs.com/magazine/chemistry-and-the-aquarium-the-relationship-between-alkalinity-and-ph/

 

[Gigajoulz]

Hydroxide is counted in an alk test. It need not do anything to be counted.

In point of fact, it also almost instantly combines with bicarbonate to form carbonate, as well as some other things such as combining with CO2/carbonic acid. But none of those processes change alkalinity.

Hydroxide consumes a bit over twice as much CO2 as does carbonate as it is converted into bicarbonate, which is the main contributor to all in seawater.

I discuss these issues in great depth here:

https://reefs.com/magazine/chemistry-and-the-aquarium-the-relationship-between-alkalinity-and-ph/

Thank you for the article! It was a big help understanding how bicarb and carb work together to buffer the pH. Can you clarify how adding bicarb can drive off CO2, later raising pH? Does this cause the alkalinity to rise or drop temporarily until the pH and CO2 stabilize? I use a skimmer on 24/7 (I think its a little underrated for my system for skimming, but I think reaches the equilibrium with the atmosphere).

I've been doing apprx 5ml of Red Sea Alk+ (which should be 0.1 dKH/1ml @ 25 gal, so I use 5ml) every other day for about a week in my 125g tank. I started at 6.2 dKH but now its close to 10 dKH and my leptastria has closed up. the soda ash raised the from a low 7.6 to around 8.0 pH like I wanted, but I think that caused the system to suck up CO2, significantly raising the Alk.

(I am an InfoTech person learning as best I can - I thank you for your patience as I dumb it down lol)

 

[Randy Holmes-Farley Verified Community Expert]

Adding bicarbonate has a small pH lowering effect when first added due to come of it becoming carbonate:

HCO3- --> H+ + CO3--

Some of it also becomes CO2, that can be blown off from the tank, and that will slowly raise pH toward a new pH and alk equilibrium as shown below:

So the new effect is a small pH drop followed by a possible pH rise if you aerate and blow off the newly excess CO2.

None of these processes impact alkalinity. Once added, it does not change.

 

[Randy Holmes-Farley Verified Community Expert]

the soda ash raised the from a low 7.6 to around 8.0 pH like I wanted, but I think that caused the system to suck up CO2, significantly raising the Alk.

You seem to be stuck on the false idea that alk later rises well after the initial addition. Nothing does that, unless you dose an organic compound that decomposes to add alk, such as the formate in AFR or the acetate in Salifert All in One.

 

[Gigajoulz]

You seem to be stuck on the false idea that alk later rises well after the initial addition. Nothing does that, unless you dose an organic compound that decomposes to add alk, such as the formate in AFR or the acetate in Salifert All in One.

I agree, maybe I'm overthinking how/if CO2 contributes to alk or how it is buffered by alkalinity in terms of hydroxide dosing. Is it the H off the carbonic acid that contributes, and CO2 is converted sf

Reading your article again and these parts really stand out to me:

At about pH 8.9 in seawater at 25 °C there are equal concentrations of HCO3(-) and CO3(-). At lower pH, there is less CO3(-), and at pH 8.0 there is really quite little carbonate in seawater (only about 4% of the bicarbonate level).

-when adding a base
HCO3(-) and CO3(-) + OH(-) → less HCO3(-) and more CO3(-)
-where the hydroxide turns some bicarb into carb, removing H+ and raising pH

-when adding an acid
HCO3(-) and CO3(-) + H(+) → more HCO3(-) and less CO3(-)
-where the carbonic acid turns some carb into bicarb, adding H+ and some bicarb, and lowing pH ...but this only happens until the tank reaches equilibrium with the atmospheric CO2 right, at which point the alk is stable? this is where I'm confused thinking the alk may change but if my system is equilibrated then I should be getting as much CO2 as I'm gonna get in there.

In my case my pH is hardly above 8.0 so I take it that most of my alkalinity is bicarb, which explains why adding 0.1 dKH of sodium carbonate doesn't raise the pH more than 0.15+/- pH (in my system that would be 5ml of RedSea Alk+ in 125gallons w/ skimmer) and then it drops back down to around 8.05 after about half a day.

 

[Gigajoulz]

I'm missing what happens to the carbonic acid after it dissociates, given a lower pH where buffering acid is harder to do, as well as what happens to the alkalinity or pH to cause CO2 to off gas (like what changes in alk or acidity causes this.)

 

[Randy Holmes-Farley Verified Community Expert]

As a general principle (it actually has a specific name) adding or removing CO2 cannot ever raise or lower alkalinity in any amount.

The alk is stable before during and after all of the reactions mentioned above. None of them impact alkalinity, just which specific chemicals add up to the same alkalinity.

Bicarbonate provides most of the alk in any reef tank at any pH it normally encounters.

The lower the pH is, the larger will be the pH rise when adding carbonate.

 

[Gigajoulz]

As a general principle (it actually has a specific name) adding or removing CO2 cannot ever raise or lower alkalinity in any amount.

The alk is stable before during and after all of the reactions mentioned above. None of them impact alkalinity, just which specific chemicals add up to the same alkalinity.

Bicarbonate provides most of the alk in any reef tank at any pH it normally encounters.

The lower the pH is, the larger will be the pH rise when adding carbonate.

After adding alk (bicarb, carb or hydroxide) does the tank re-equilibrate to the CO2 levels in the air or is that like a one time thing as you bring a skimmer online? On one hand, I want higher pH with less additions of alk so I think hydroxide is the way to go, but on the other hand the hydroxide does the same alk as bicarb. Theres a cog thats not turning for me among all this

 

[BigMonkeyBrain]

After adding alk (bicarb, carb or hydroxide) does the tank re-equilibrate to the CO2 levels in the air or is that like a one time thing as you bring a skimmer online? On one hand, I want higher pH with less additions of alk so I think hydroxide is the way to go, but on the other hand the hydroxide does the same alk as bicarb. Theres a cog thats not turning for me among all this

After adding an alk supplement --> the alk increases and then remains the new level. If adding Bicarbonate with H+ (NaHCO3 ) the addition lowers the PH a bit after adding it to the tank until the excess H+ combines with maybe O to make H2O and excess C02 that is blown off to equilibrate to the surrounding air C02.

The C02 level changes the PH not the level of alk in the tank.


Probably happens !

“So let it be written, so let it be done”

 

[Gigajoulz]

After adding an alk supplement --> the alk increases and then remains the new level. If adding Bicarbonate with H+ (NaHCO3 ) the addition lowers the PH a bit after adding it to the tank until the excess H+ combines with maybe O to make H2O and excess C02 that is blown off to equilibrate to the surrounding air C02.

The C02 level changes the PH not the level of alk in the tank.


Probably happens !

“So let it be written, so let it be done”

so if carbonic acid adds H+ to the water and doesn't change alk, how does hydroxide add OH- to the water without changing alk? does the hydroxide force the system's bicarb alk to convert to carb, and that carb takes a H+ donated by carbonic acid (raising pH)?

what happens to the rest of the carbonic acid without the one H+? the HCO3- ? isn't this < a component of bicarb, or no because its missing sodium?

 

[BigMonkeyBrain]

so if carbonic acid adds H+ to the water and doesn't change alk, how does hydroxide add OH- to the water without changing alk? does the hydroxide force the system's bicarb alk to convert to carb, and that carb takes a H+ donated by carbonic acid (raising pH)?

what happens to the rest of the carbonic acid without the one H+? the HCO3- ? isn't this < a component of bicarb, or no because its missing sodium?

We will need Randy on this ! There is much more to Alk ( buffer ) than carbonate, like borate and many more different molecules. The H+ can move from carbonic acid, this chemical atom exchange is instant. "H₂CO₃ , The molecule rapidly converts to water and carbon dioxide in the presence of water." Wikipedia

The molecules you are talking about and the Alk are in solution at a certain level and the level like 8-dkh will not change by moving ions around. If an acid is added to the same solution or molecules are used by calcification or buffering in the sand bed then the Alk level will change.

Probably happens !

“So let it be written, so let it be done”

 

[Randy Holmes-Farley Verified Community Expert]

If you want the highest pH boost per unit of alk added, hydroxide is the winner. Carbonate is second best. Bicarbonate won’t boost pH.

They can all add the same alk. Only the pH effect is different.

As I said CO2, which is the same as carbonic acid when in water, cannot add or deplete alk.

CO2 + H2O —> H2CO3 (carbonic acid)

H2CO3 —> H+ + HCO3-

The H+ lowers alk and the bicarbonate adds alk and they exactly offset.

Adding hydroxide adds alk instantly, and can convert into bicarbonate by combining with carbonic acid.