kalkwasser question

[takayan]

If you drip too fast or if there is not enough Carbon Dioxide available in the water, your shiny new Bicarbonate ions will be converted to Carbonate ions (a bad thing), like this:

Ca++ + 2(OH-) + 2(HCO3-) <==> Ca++ + 2(CO3--) + 2 H2O

Why this reaction is not good?
https://www.saltcorner.com/Articles/Showarticle.php?articleID=91&i=1

 

[KrisReef]

Lowers pH, wastes bio-available alkalinity instead of raising it.

 

[takayan]

I understand the pH part, but not for carbonate part. I thought corals take carbonate for calcification.

 

[Randy Holmes-Farley Verified Community Expert]

That reaction as written is no concern.

That said, the main problem at high pH with any sort of alk and calcium addition is that you can precipitate calcium carbonate more rapidly than at lower pH.

It is a somewhat unanswered issue in reefing, IMO, whether any individual coral takes up bicarbonate and converts it to carbonate, or directly takes up carbonate. It is actually quite challenging to technically make the distinction, and I have never seen any publication where scientists tried.

Regardless, the bicarbonate to carbonate ratio depends ONLY on pH, not on other things like how you got there.

 

[sayurasem]

First time kalkwasser dosing here, I’ve been dosing 960ml max saturation kalkwasser during lights out. 1:00am - 8:30am every 30 mins, 60ml per dose. My doser takes right under 3 minutes to dose all 60ml at once.

Here are my results:
91gal system, 75gal net water vol.
1/14 kh: .42 8.9 10:30pm
Cal: .16 420
Mag: .14 1290

1/15 960ml kalk over night
Ph: 7.7 10:30am
Kh: .42 8.9
Cal: .18 410
Mag: .14 1290

It seems the article explain why kalkwasser is not doing anything to my tank. I’m dosing kalkwasser too fast.

 

[Randy Holmes-Farley Verified Community Expert]

First time kalkwasser dosing here, I’ve been dosing 960ml max saturation kalkwasser during lights out. 1:00am - 8:30am every 30 mins, 60ml per dose. My doser takes right under 3 minutes to dose all 60ml at once.

Here are my results:
91gal system, 75gal net water vol.
1/14 kh: .42 8.9 10:30pm
Cal: .16 420
Mag: .14 1290

1/15 960ml kalk over night
Ph: 7.7 10:30am
Kh: .42 8.9
Cal: .18 410
Mag: .14 1290

It seems the article explain why kalkwasser is not doing anything to my tank. I’m dosing kalkwasser too fast.

No, please ignore that article.

You are dosing plenty slow enough, assuming it is to a high flow area.

Why is the explanation any more than if you want alk to increase, you need to dose more than the daily demand?

You are only dosing 0.3 dKH of alk each night.

Even with no demand, that would be hard to see in one day.

 

[sayurasem]

No, please ignore that article.

You are dosing plenty slow enough, assuming it is to a high flow area.

Why is the explanation any more than if you want alk to increase, you need to dose more than the daily demand?

You are only dosing 0.3 dKH of alk each night.

Even with no demand, that would be hard to see in one day.

Dosing kalk into return chamber with wavemaker. My doser would only dose a maximum of 999ml per head, per day. I want to switch to kalk to reduce cost and because of my low ph. I guess I will have to get a proper doser and report back.

 

[sayurasem]

I would also hope at the very least see a bump in ph during lights out.

 

[Randy Holmes-Farley Verified Community Expert]

I would also hope at the very least see a bump in ph during lights out.

Well, no. 0.3 dKH is much too small to see any significant pH effect over those hours, and the above article cannot explain it even if it were actually correct.

Ca++ + 2OH- this is dosed in kalkwasser

But what can precipitate is CaCO3

to get from Ca++ and 2 OH- to CaCO3 MUST consume CO2:

2 OH- + CO2 --> CO3-- + H2O

So you would get a pH increase (reduction of CO2) even if you precipitated calcium carbonate instantly.

In the end, that is what happens anyway with corals. They deposit calcium carbonate skeletons.

 

[sayurasem]

Well, no. 0.3 dKH is much too small to see any significant pH effect over those hours, and the above article cannot explain it even if it were actually correct.

Ca++ + 2OH- this is dosed in kalkwasser

But what can precipitate is CaCO3

to get from Ca++ and 2 OH- to CaCO3 MUST consume CO2:

2 OH- + CO2 --> CO3-- + H2O

So you would get a pH increase (reduction of CO2) even if you precipitated calcium carbonate instantly.

In the end, that is what happens anyway with corals. They deposit calcium carbonate skeletons.

I see, thank you. May I ask if there is a calculator for dKH per gallon for kalkwasser dosing? I really want to make this work.

 

[sayurasem]

I’m not going to dose two part today and will test again tonight to see how much dKH is my tank consuming per day.

 

[Randy Holmes-Farley Verified Community Expert]

I see, thank you. May I ask if there is a calculator for dKH per gallon for kalkwasser dosing? I really want to make this work.

Yes:

https://reef.diesyst.com/chemcalc/chem_calc3.html

 

[sayurasem]

Yes:

https://reef.diesyst.com/chemcalc/chem_calc3.html

Thank you, what would you say is the max dose per 30mins/1 hour? Given the speed of my doser is 20ml/ min.