Kalkwasser and a low carbon dioxide environment?

[ReefNerd]

300 Liter Mixed Reef
Salinity - 1.027
Alk - 7DKH (target) daily drop despite Kalk dosing, 1.5DKH
Calcium - 420ppm
Nitrate - 0 - 0.5 (I dose a small amount every day and its consumed by the next day)
PH - 8.3-8.5
Temp - 25 Celsius

I have a 25L auto top off, and have been running 40g of Kalk in it, the 25L last exactly 1 week at my current rate of evaporation. Just yesterday I changed my dose to 50grams of Kalk, 200ml of Vinegar and 25L of RODI.

I run the Santa Monica Rain 2 ATS, it produces ~50-60 grams of squeezed Green Algae per week

I have a question regarding the use of Kalkwasser in a tank with an Algae Turf Scrubber, does anyone have any experience with this? I am finding my ALK is dropping really fast and the Kalkwasser cant keep up, im running maximum saturated Kalk in my auto-top off.

Just yesterday I added some white vinegar and additional Kalk to over-saturate it and make it stronger... Is it that my tank is just too full now and I have outgrown Kalk? Or is something else at play here? I have seen pictures of tanks as heavily stocked as mine (or more) with people who just run Kalk... but for me it doesn't even remotely keep up? (I am manually dosing 7grams of Sodium Bicarbonate in a mixed in small amount of RODI every day to bring it back up)

Is it possible that the ATS is consuming too much carbon dioxide from the water and therefore preventing the reaction with Kalk that produces Alkalinity? Effectively drastically reducing the potency of my Kalk? I'm no chemist but I am struggling to understand how Kalk doesn't even appear to be making a dent in my Alk consumption. Its dropping roughly 1-2 DKH a day despite the ~3.75 Liters of saturated Kalk being added a day.

Contibuting factors to my theory of low carbon dioxide are

• no fish in the tank (they are in quarantine tank right now due to Ich outbreak a month or so ago)
• ATS grows rapidly, ~50grams squeezed green hair algae per week
  
• no-one is home during the day
• at night only I am home and sleep in a different room
• there are some pot plants my the apartment

I am eager to test tonight to see if the vinegar has made any difference or if my Alk is going to be super low again...

 

[Dsnakes]

That is a beautiful tank the C02 is not something I’ve heard of before in this concept of effecting the reef tank.

 

[ramona]

Awesome tank! Can you post pictures of your sump? Thank you

 

[sghera64]

Adding / removing CO2 does not affect alkalinity.

Vinegar is an acid and will consume alkalinity. Stony coral growth produces acid as a growth bi-product which will also depress alkalinity. Additionally, stony corals consume calcium and carbonate, further depressing alkalinity.

Perhaps your low alkalinity levels are not a problem, but actually signs of great coral health and growth.

 

[sghera64]

A few questions for you regarding your kalkwasser make-up.

1. Did you add the vinegar to the Kalk?
2. Are you using a Neilson reactor do dose the Kalk, or do you make the kalk up in a batch container and then draw out of that to put into the tank?
3. I presume you are using RO/DI water to mix the Kalk. How long has that water been exposed to air prior to mixing it with Kalk?

 

[Randy Holmes-Farley Verified Community Expert]

300 Liter Mixed Reef
Salinity - 1.027
Alk - 7DKH (target) daily drop despite Kalk dosing, 1.5DKH
Calcium - 420ppm
Nitrate - 0 - 0.5 (I dose a small amount every day and its consumed by the next day)
PH - 8.3-8.5
Temp - 25 Celsius

I have a 25L auto top off, and have been running 40g of Kalk in it, the 25L last exactly 1 week at my current rate of evaporation. Just yesterday I changed my dose to 50grams of Kalk, 200ml of Vinegar and 25L of RODI.

I run the Santa Monica Rain 2 ATS, it produces ~50-60 grams of squeezed Green Algae per week

I have a question regarding the use of Kalkwasser in a tank with an Algae Turf Scrubber, does anyone have any experience with this? I am finding my ALK is dropping really fast and the Kalkwasser cant keep up, im running maximum saturated Kalk in my auto-top off.

Just yesterday I added some white vinegar and additional Kalk to over-saturate it and make it stronger... Is it that my tank is just too full now and I have outgrown Kalk? Or is something else at play here? I have seen pictures of tanks as heavily stocked as mine (or more) with people who just run Kalk... but for me it doesn't even remotely keep up? (I am manually dosing 7grams of Sodium Bicarbonate in a mixed in small amount of RODI every day to bring it back up)

Is it possible that the ATS is consuming too much carbon dioxide from the water and therefore preventing the reaction with Kalk that produces Alkalinity? Effectively drastically reducing the potency of my Kalk? I'm no chemist but I am struggling to understand how Kalk doesn't even appear to be making a dent in my Alk consumption. Its dropping roughly 1-2 DKH a day despite the ~3.75 Liters of saturated Kalk being added a day.

Contibuting factors to my theory of low carbon dioxide are

• no fish in the tank (they are in quarantine tank right now due to Ich outbreak a month or so ago)
• ATS grows rapidly, ~50grams squeezed green hair algae per week
  
• no-one is home during the day
• at night only I am home and sleep in a different room
• there are some pot plants my the apartment

I am eager to test tonight to see if the vinegar has made any difference or if my Alk is going to be super low again...

Higher pH increases demand for calcium and alk, and limewater often cannot keep up.

 

[Randy Holmes-Farley Verified Community Expert]

Stony coral growth produces acid as a growth bi-product which will also depress alkalinity.

What exactly do you mean by that? What are they producing?

 

[Randy Holmes-Farley Verified Community Expert]

Is it possible that the ATS is consuming too much carbon dioxide from the water and therefore preventing the reaction with Kalk that produces Alkalinity? ...

No. Even straight limewater (kalkwasser) will give a proper result with an alk titration, and it readily mixes into the carbonate system nearly instantly unless the pH is way above 9.

pH is also a perfect indicator of carbon dioxide levels. Unless the pH is excessively high, there is no shortage of CO2.

 

[sghera64]

What exactly do you mean by that? What are they producing?

As I understand it, as one bicarbonate is taken up by the coral one hydrogen ion (acid) is released back into the water.

Do I have that wrong?

 

[LC8Sumi]

I have the very same problem in a very similiar tank (RS Reefer 250 + 25l Fuge). Alk is dropping insanely with using fully saturated kalk in my ATO. I have to dose another ~80ml of fauna marin carbonate mix if I want to keep it at 8 dKh. Without kalk I had to dose 96ml of the solution daily to keep it at this level, and 12ml of calcium (RS Reef foundation A liquid). Once I stop dosing, and rely only on the kalk it's dropping crazy (1.5dKh a day). I also have a refugium on reverse cycle, and monitor my pH with an Atlas probe that also acts as a controller so it shuts off the ATO at pH 8.3. I also pull the skimmers air from the outside.

My calcium and magnesium is somewhat stable without dosing, Ca sits at 380-400 ppm since transfering to kalk and Mg is at 1320 ppm. It's almost like something is pulling out alk much faster than kalk could keep up with, while it (kalk) can keep up with the calcium demand.

I do weekly 10% water changes with Red Sea blue bucket @ 35ppt.

Anyway, this is how my pH is during the day (the end of the graph is tricky, as that is when my ATO kicked in after some blockage in the sensor midday). The trend is pH 7.9 before the lights come on, and 8.3 when the main T5's are switched off and leds are ramping down. The T5's come on at 1PM and are switched off at 7PM. Pretty much linear rising between 7AM and 7PM, then dropping linear from 7PM to 7AM. It's funny actually that how T5's have a much larger effect on the pH than the LEDs, but I guess that is a different story.

 

[ReefNerd]

No. Even straight limewater (kalkwasser) will give a proper result with an alk titration, and it readily mixes into the carbonate system nearly instantly unless the pH is way above 9.

pH is also a perfect indicator of carbon dioxide levels. Unless the pH is excessively high, there is no shortage of CO2.

Okay good to know, thanks.

I tested Alk last night, 24 hours after running my vinegar+kalk mix in my ATO and my Alk was at 7.1, ill test again tonight and hopefully not see it at 5.5-6 or something too low like I have been.

If its still dropping, I can increase the over-saturation of kalk a bit more. My current batch is 200ml vinegar, 50 grams kalk, 25L RODI. So I believe there is still a bit more headroom to super saturate it with more vinegar and kalk in my 25L RODI container. If that still fails to prevent the decline, I guess I will have to accept that I need to migrate to dosing 2 part and invest in a doser...

 

[ReefNerd]

Okay got home and tested

Alk 7.3
Ca 425
Mg 1365

its only been 48 hours but looking promising... Alk actually went up for the first time ever...

It seems the vinegar and extra potency it allows was all the difference. Ill continue monitoring for the next few days and see if it stabilizes or keeps going up... in any case first day in weeks that I haven't had to dose manually to restore levels

 

[LC8Sumi]

I'll try this recepie.. How strong vinegar did you use? We have 10%, 15% and 20% strong ones in this country.

 

[ReefNerd]

I'll try this recepie.. How strong vinegar did you use? We have 10%, 15% and 20% strong ones in this country.

I used Cornwells White Vinegar which is a common brand here in Australia. It does not say what the acid concentration is, I found a student research project online from 2005 that tested it and found it to be 6.8%.

Most of the articles I have seen around Kalk and vinegar assume a 5% concentration. So for you I think you should use the 10% one you have access to and take that into account?

 

[LC8Sumi]

I might as well use a 10% one with 1:1 RODI dilution. So 100ml vinegar, 100ml rodi, 50gram Ca(OH)2, 25liter RODI

 

[ReefNerd]

I might as well use a 10% one with 1:1 RODI dilution. So 100ml vinegar, 100ml rodi, 50gram Ca(OH)2, 25liter RODI

The actual formulas and stuff are in some of Randy's articles, but I napkin math calculated based on his examples of a recommended dose and then converted it all to be based off 25Litres of of RODI

"One reasonable point to shoot for is to add about the same amount of total CO2 via the vinegar as is needed by the lime to form HCO3-. This balance is roughly matched by using three level teaspoons of solid lime per gallon of limewater, and 45 ml of vinegar per gallon of limewater. For those aquarists choosing to use vinegar in limewater, these values are a suitable starting point."

I dislike "teaspoons" being used as a unit of measurement. It's inaccurate and a teaspoon is actually a unit of liquid volume not weight. For this purpose a level teaspoon is ~3 grams of kalk. Generally Kalk is cited as saturated at 2 teaspoons or 6 grams per 1 gallon (1 gallon is 3.7 liters, I round to 4 below)

So my maths:
Saturated Kalk for 25L of RODI is 40 grams - (25/4) * 6 = 37.5 (i round to 40 grams as this is supported by this kalk calculator https://www.hamzasreef.com/Contents/Calculators/KalkContribution.php )
+50% (2 teaspoons plus 1) would be 9 grams per 4 Liters
(25/4) * 9) = 56.25 grams of kalk

Randy reccommended 45ml of vinegar per gallon at 3 teaspoons of Kalk
So... 45ml / 4L = 11.25ml per Liter * 25 = 281.25ml
I rounded this up because a gallon is actually 3.7Liters; therefore came out at a recipe of 300ml of vinegar, 56.25 grams of kalk, 25liters of RODI

To be conservative and to give me some additional headroom, I selected my first dose (now in place for 2 and a half days) to be 200ml of vingar, 50 grams kalk, 25 liters of RODI

 

[SteadyC]

I do kalk, I used to have an ATS but I moved to chaeto, with a mixed reef tank, and I do have to supplement with some sodium carbonate daily. I’m still happy with kalk for its simplicity, PH effect, and thus far is keeping up with calcium demand on its own. I don’t mind dosing some sodium carbonate daily, it’s on a dosing pump, and is doing roughly an additional 14ml daily. If kalk wasn’t keeping up with calcium demand also, I might evaluate changing.

I used to use a container with kalk, separate from main ATO, and add vinegar also. But, I’ve moved to a stirrer, much easier.

 

[HereFishyFishyFishy!]

Adding / removing CO2 does not affect alkalinity.

Vinegar is an acid and will consume alkalinity. Stony coral growth produces acid as a growth bi-product which will also depress alkalinity. Additionally, stony corals consume calcium and carbonate, further depressing alkalinity.

Perhaps your low alkalinity levels are not a problem, but actually signs of great coral health and growth.

Yes, it does. Google CO² and acid base balance in aquariums.

 

[Randy Holmes-Farley Verified Community Expert]

Yes, it does. Google CO² and acid base balance in aquariums.

No it doesn’t.

Adding it removing CO2 has no impact on alkalinity.I think you are confusing pH and alkalinity.

FWiW, this also is a 5 year old thread.

 

[Randy Holmes-Farley Verified Community Expert]

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.