Reef chemistry calculator off?

[Floyd-]

How accurate is the reef calculator in the sticky? Ive been dosing per that and it seems to never be enough.
For example im trying to raise my alk. I was at 7.4 and im trying to get up to 9 dHK. Ive used the calculator 3 times and dosed what it said and even after 3 days im only at 7.9 and no where near 9 like im trying to get to.
Are my corals just using it up THAT FAST! or is the calculator off?

 

[Duffer]

most likely your tank is using up more than you are dosing

 

[shwareefer]

Your tank inhabitants plus CO2 are using it.

 

[Randy Holmes-Farley]

Your tank inhabitants plus CO2 are using it.

Not sure what you mean by that, but CO2 does not combine with alkalinity to deplete it.

 

[Floyd-]

How much is ok to add at once? Im using the liquid brightwell 8.3 product. If I go by the bottle it states no more than 5ml a day (I think thats nuts)
I have been dosing about 16ml a day and its barely moving.

 

[Randy Holmes-Farley]

How accurate is the reef calculator in the sticky? Ive been dosing per that and it seems to never be enough.
For example im trying to raise my alk. I was at 7.4 and im trying to get up to 9 dHK. Ive used the calculator 3 times and dosed what it said and even after 3 days im only at 7.9 and no where near 9 like im trying to get to.
Are my corals just using it up THAT FAST! or is the calculator off?

Highly unlikely the calculator is off, but you might be entering thigns wrong.

What exactly did you use and what did you enter to the calculator and dose?

Certainly, tanks can easily use 2 dKH in a day.

 

[Randy Holmes-Farley]

How much is ok to add at once? Im using the liquid brightwell 8.3 product. If I go by the bottle it states no more than 5ml a day (I think thats nuts)
I have been dosing about 16ml a day and its barely moving.

What size aquarium?

 

[Floyd-]

I have a 45 gallon tank going from 7.4 to 9 dHK with the brightwell 8.3 fluid. I think it was 16ml that it stated to use.
I do have a bit of coral in this tank so maybe its just using it that fast!

 

[Floyd-]

Looking at it now again. States 23.3ml to get from 7.4 to 9dHK.
Ive been putting nearly 20ml a day in this little tank and its not moving much.
Guess I should look into a dosing pump setup because adding it manually every day SUCKS.

 

[Randy Holmes-Farley]

16 mL is only a bit over 1 dKH in your aquarium. It can easily be using that much.

That is certainly not an upper limit to dosing. You can dose much more if needed.

 

[shwareefer]

Not sure what you mean by that, but CO2 does not combine with alkalinity to deplete it.

Thanks. I thought low PH counteracts alkalinity and since Co2 lowers PH, that was the correct way to phrase it. Is that wrong too?

 

[Randy Holmes-Farley]

Thanks. I thought low PH counteracts alkalinity and since Co2 lowers PH, that was the correct way to phrase it. Is that wrong too?

Elevated CO2 lowers pH, but has no effect on alkalinity.

This article has the more detailed explanation:

Chemistry and the Aquarium: What is Alkalinity?

Randy provides an overview of alkalinity as to why it's important, how it's measured, and how can it be tested.

reefs.com

Alkalinity Facts
There are several facts about total alkalinity that follow directly from the definition. Unfortunately, some of these have been misunderstood by some hobby authors.

One of these facts is termed The Principle of Conservation of Alkalinity by Pankow (“Aquatic Chemistry Concepts”, 1991). He shows mathematically that the total alkalinity of a sample CANNOT be changed by adding or subtracting CO2. Unfortunately, there is an article available on line, which claims otherwise, and encourages people to “lower alkalinity” by adding CO2 in the form of seltzer water. This is simply incorrect.

Forgetting the math for the moment, it is easy to see how this must be the case. If carbonic acid is added to any aqueous sample with a measurable alkalinity, what can happen?

Well, the carbonic acid can release protons by reversing equations 1 and 2:

(5) H2CO3 ==> H+ + HCO3–

(6) HCO3– ==> H+ + CO3—

These protons can go on to reduce alkalinity by combining with something that is in the sample that provides alkalinity (carbonate, bicarbonate, borate, phosphate, etc). However, for every proton that leaves the carbonic acid and reduces alkalinity, a new bicarbonate or carbonate ion is formed that adds to alkalinity, and the net change in total alkalinity is exactly zero. The pH will change, and the speciation of the things contributing to alkalinity will change, but not the total alkalinity.

This is not true for strong acids, however. If you add hydrochloric, sulfuric or phosphoric acids (or any acid with a pKa lower than the carbonic acid endpoint), there will be a reduction in the alkalinity.

 

[Floyd-]

16 mL is only a bit over 1 dKH in your aquarium. It can easily be using that much.

That is certainly not an upper limit to dosing. You can dose much more if needed.

How much max would be safe to dose at once? Again I was worried because the bottle states no more than 5ml a day.
Could I toss in 30ml and be safe? Toss it all in at once or spread it out?

 

[Randy Holmes-Farley]

How much max would be safe to dose at once? Again I was worried because the bottle states no more than 5ml a day.
Could I toss in 30ml and be safe? Toss it all in at once or spread it out?

There is no max "safe" dose of alkalinity supplement, but if you are clearly adding more than the organisms in the tank might possibly be using, then it may be cause to check that there is no big problem with abiotic precipitation of calcium carbonate. Some precipitation is normal, but if it gets excessive (hardening sand, clogged pumps, etc.) then it may be time to look to break the precipitation cycle.

FWIW, coralline algae alone can use a lot, and 2 dKH a day even in a soft coral tank is not necessarily a problem.

 

[Duffer]

How much max would be safe to dose at once? Again I was worried because the bottle states no more than 5ml a day.
Could I toss in 30ml and be safe? Toss it all in at once or spread it out?

Are you sure it states that, The reason i ask is i never seen that on raising alk for dosing, what i usually see on bottles is don't raise it more than .5 per day.

 

[Floyd-]

Wow! This whole time I was thinking I was doing something wrong.
Thanks for the info Randy.