Kalkwasser not raising alk or ph

[george7523]

Hi Randy,

I'm testing to dose kalk, and after test running it for a day, I find it not raising my alk or ph for some reason. I've done a fair bit of research and setup wise I think it's pretty ideal. I read your limewater article too. extremely helpful.

here's my setup.

- 10 gallon display + 13 gallon sump = 23 gallon total.
- daily alk consumption using triton core 7 is 1 dkh. about 0.1 dkh per hour during day time. I normally dose triton core 7 from 9am to 9pm only.
- mixed reef containing sps and zoas and softies.

- according to reef calculator. I need to be dosing 70ml per hour to raise 0.1 dkh. (This is below my evaporation rate) So I set my ghl doser to dose 12ml every 10 minutes (12 x 6 = 72ml) at the slowest dosing head speed of (4.3ml per minute)

- I mix 3 gallon rodi with 12 tsp of brightwell kalk+2. I wanted to ensure the rodi is saturated so I double dose (4 tsp as oppose to the recommended 2tsp per gallon) and expected slurry to form at the bottom and it does. the container is diy glass with top cover. I have two magnetic stirrers beneath the glass tank for mixing. the intake tubing sits about 1 inch above the bottom to prevent sucking up slurry at the bottom. just to be safe I taped edges of the cover to give it more seal. I mix with magnetic stirrer with the covers closed and sealed up for a good couple of hours and let it sit another couple of hours before starting to dose.

I also have a alkatronic that is in working order ( all pumps and probe recently calibrated) to monitor alkinlinty. I also have hanna alk checker for reference.

with this setup, I observe my alk slowly decrease by the hour as I dose 12ml every 10 minutes. frustrated, I even tried dosing kalk slurry (3 gallon + 12 tsp) by leaving the magnetic stirrer on while dosing. even with slurry, my alk still decreases. I then try dosing after the lights go off, which doesn't consume alk and should stay the same (8.0dkh) until lights go on again the next morning. But dosing kalk after lights go off makes the alk decrease as well. I don't think it's precipitating out in the sump as the dosing tube sits right above a wavemaker in the refugium and the opposing side has another wavemaker flowing opposite way. so there should be enough mixing to prevent precipitation. I'm kind of at a loss. can someone give some suggestion as to what I'm missing ?

I'm attaching some pictures of my setup and a video of dosing in progress.

video link :
https://photos.app.goo.gl/EcmzViv6a5vnzDFq9

thanks alot for helping.

 

[george7523]

update:

I just measured the Ph of the saturated kalk in the reservoir. It's 12.051 ph. So it's full potency saturated kalk I'm dosing.

 

[arking_mark]

What is the pH of your tank while dosing?

 

[nereefpat]

You could be underestimating alkalinity demand.
Another thing that happens with kalk is that the more you dose, the more demand goes up due to higher pH and higher alk.

Are you performing an offline alk test with a kit like Salifert or API? If so, and they confirm your alk results, I would just up the dose.

 

[george7523]

I see. Thank you both for your feedback. But can alk demand rise so quickly ? As I've only started dosing kalk one day. Yes, I use Hanna alk test every 3 hour to verify alkatronic. While dosing my tank's ph goes from around 8.0 at light on to about 8.2 at lights off. But this rise in pH is what I normally observe without dosing kalk. I wonder if I'm just not dosing enough of it ? Or does it have something to do with the slowest dosing head speed I selected (4.3ml per minute) which I thought would be desirable. But I vaguely remember in telegraham and reefdudes YouTube video




about kalkwasser they mention when dosing too slowly might be problematic. But as I previously stated that according to reef calculator, 23 gallon , 1dkh daily consumption, 0.1 dkh hourly consumption, requires 70ml hourly dose or 770ml daily dose. So I dose 12ml per 10 minutes (12ml x 6 = 72ml hourly) from 9am to 9pm (72ml x 12hour = 864ml). The calculation seems ok to me. Not sure if I can dose more then 12ml per 10minutes as I'm approaching my evaporation limit. I might have to add a fan to increase my evaporation rate. Thanks for input. Appreciate it.

 

[nereefpat]

Your math looks right to me too. I think you're doing everything right. For me, kalk does take some trial and error.

I would try upping the dose a little bit.

 

[Randy Holmes-Farley]

update:

I just measured the Ph of the saturated kalk in the reservoir. It's 12.051 ph. So it's full potency saturated kalk I'm dosing.

Not so fast.

If your pH value is accurate, it's very dilute. Much less than 50% potent.

Saturated limewater at 25 deg C has a pH of 12.54, and the scale is logarithmic so 0.3 pH units is about a factor fo 2.

Conductivity is a better way to gauge potency. 10.3 mS/cm is about saturated at 25 deg C. Potency is roughly linear with conductivity.

 

[george7523]

Ok thanks nereefpat. I will increase the dose. Like you said trail and error. Sidenote : I actually even dosed "kalk slurry" in my desperation at one point by leaving the magnetic stirrer on while dosing (3 gallon rodi + 12 tsp kalk) Same result of no ph boost , and slow alk decline from 8.0 to 7.5 at around 2pm. It would've gone even lower to 7.0 I'd imagine but I intervened by dosing my regular triton core 7

 

[Randy Holmes-Farley]

It is entirely possible that limewater cannot meet the demand in your tank.

it is also common for kalk stirrers to deliver a weak brew.

Adding 1.4 dKH of alk via limewater will instantly boost the pH by 0.6 to 0.7 pH units. If you spread that out, the rise is much smaller.

 

[george7523]

@Randy thank you for your insight ! I would've never caught that. Definitely will see if I can correct that. I wonder what I'm doing wrong though. I first pour 3 gallon rodi into the reservoir. Added the kalk to it. As it floats on top of the water surface. I spent about 20 seconds using a stick make it go down into the water column. I then close the cover which closes very snug. But I tape its edges up anyway to seal it even further. I then turn on 2 magnetic stirrer on for about 2 hours. Let's say if somehow enough CO2 does get in and the kalk becomes diluted which in fact it has happened according to the measured pH. Can I simply "recharge" it by adding more kalk and stir it again ? Or does the exposure to CO2 dilution make the existing water no longer able to be recharged and I should get rid of it and use another 3 gallon of fresh rodi to make a new batch of saturated kalk ?

Sidenote : @Randy I have read your excellent limewater article and the pH test you conducted on your closed brute trash can kalk reservoir over time shows that I should not have potency loss. But let's just assume that it somehow happened in my case. ( Or maybe magnetic stirrer not effective enough at mixing )

 

[Randy Holmes-Farley]

How much solid added to the 3 gallons of RO/DI?

For a baseline pH measurement, put 2 tablespoons calcium hydroxide in a cup of RO/DI and mix a few min and measure the pH of that. Then compare the kalkwasser pH to that saturated solution. You can roughly gauge potency by the difference in pH.

 

[george7523]

I purposely added double the amount required for saturated kalk. So 3 gallon x 2 tsp x 2 = 12 tsp added.

Ok I will try that and get a baseline reading and report back. Thanks Randy.

 

[Randy Holmes-Farley]

OK, sounds good.

 

[george7523]

Hi Randy,
Mixing the 2 tsp kalk + 1 cup rodi gave me a baseline pH reading of 12.329. The 3 gallon saturated kalk was previously measured at 12.051. the difference is 0.278 pH. So the saturated kalk is quite dilute as you stated since pH is logarithmic. I took a measure of the 3 gallon saturated kalk again, and after 4 days of sitting still and not dosing or moved the pH is now reading 11.956. So after 4 days it apparently lost 12.051 - 11.956 = 0.095 pH. I don't know if this decrease is significant or normal. I'm pretty confident the glass reservoir is adequately sealed.

 

[Randy Holmes-Farley]

Hi Randy,
Mixing the 2 tsp kalk + 1 cup rodi gave me a baseline pH reading of 12.329. The 3 gallon saturated kalk was previously measured at 12.051. the difference is 0.278 pH. So the saturated kalk is quite dilute as you stated since pH is logarithmic. I took a measure of the 3 gallon saturated kalk again, and after 4 days of sitting still and not dosing or moved the pH is now reading 11.956. So after 4 days it apparently lost 12.051 - 11.956 = 0.095 pH. I don't know if this decrease is significant or normal. I'm pretty confident the glass reservoir is adequately sealed.

It's hard to know if that drop was due to pH drift or an actual decline.

A sealed vessel of limewater shouldn't change in concentration (unless the temp changes), and I've measured a simple closed Brute trash can for a month with no decline (measured by conductivity).

 

[george7523]

Not so fast.

If your pH value is accurate, it's very dilute. Much less than 50% potent.

Saturated limewater at 25 deg C has a pH of 12.54, and the scale is logarithmic so 0.3 pH units is about a factor fo 2.

Conductivity is a better way to gauge potency. 10.3 mS/cm is about saturated at 25 deg C. Potency is roughly linear with conductivity.

Hi Randy,

Almost two months later, I found out yesterday that the measuring spoons I'd been using weren't actually teaspoon measurements. The numbers labeled on them actually refers to millimeter, not teaspoon. So all this time when I thought I was adding 12 tsp of kalk to my 3 gallon reservoir, I was actually only adding 12 ml (2.4 tsp) Which translates to 0.81 tsp per gallon. Less then half of the amount needed for full saturation (2 tsp per gallon). "Much less then 50% potent" as you put it is right on the money. You were asolutely correct in catching the solution is very dilute and not saturated at all. All this time I thought I'd been dosing kalk slurry by adding double the amount of kalk and leaving the magnetic stir bar on constantly, when in fact it's not even enough for full saturation. Always human errors. misadventures in reefing

I have since bought proper measuring spoons that actually measures teaspoon unit. And I'm adding 2 tsp per gallon as required for full saturation. My new question is, how long should I let the magnetic stir bar mix the solution for after adding fresh kalk (6 tsp) into the reservoir (3 gallon) ? After mixing for about an hour and another hour to let it settle, I'm still noticing undisolved kalk slurry at the bottom. Is this even kalk or other substance ? I read different answers in regards to the mixing time. Answers vary from a few seconds to overnight. Your input would be most appreciated. Thanks Randy !

 

[Randy Holmes-Farley]

I have since bought proper measuring spoons that actually measures teaspoon unit. And I'm adding 2 tsp per gallon as required for full saturation. My new question is, how long should I let the magnetic stir bar mix the solution for after adding fresh kalk (6 tsp) into the reservoir (3 gallon) ? After mixing for about an hour and another hour to let it settle, I'm still noticing undisolved kalk slurry at the bottom. Is this even kalk or other substance ? I read different answers in regards to the mixing time. Answers vary from a few seconds to overnight. Your input would be most appreciated. Thanks Randy !

How long to stir is a bit of guesswork when not monitoring conductivity since it depends on particle size, turbulence, etc.

Overnight is plenty. A few minutes might be enough. When I was mixing, 15-30 minutes got most of the way there.

 

[Reef.]

Hi Randy,

Almost two months later, I found out yesterday that the measuring spoons I'd been using weren't actually teaspoon measurements. The numbers labeled on them actually refers to millimeter, not teaspoon. So all this time when I thought I was adding 12 tsp of kalk to my 3 gallon reservoir, I was actually only adding 12 ml (2.4 tsp) Which translates to 0.81 tsp per gallon. Less then half of the amount needed for full saturation (2 tsp per gallon). "Much less then 50% potent" as you put it is right on the money. You were asolutely correct in catching the solution is very dilute and not saturated at all. All this time I thought I'd been dosing kalk slurry by adding double the amount of kalk and leaving the magnetic stir bar on constantly, when in fact it's not even enough for full saturation. Always human errors. misadventures in reefing

I have since bought proper measuring spoons that actually measures teaspoon unit. And I'm adding 2 tsp per gallon as required for full saturation. My new question is, how long should I let the magnetic stir bar mix the solution for after adding fresh kalk (6 tsp) into the reservoir (3 gallon) ? After mixing for about an hour and another hour to let it settle, I'm still noticing undisolved kalk slurry at the bottom. Is this even kalk or other substance ? I read different answers in regards to the mixing time. Answers vary from a few seconds to overnight. Your input would be most appreciated. Thanks Randy !

You might have since noticed but Randy suggested adding two tablespoons to a cup for a base line, you replied back that you added two tsp (teaspoons).

 

[West1]

I’ve got a question that I’m frustrated with.
I’m dosing kalk and doing 2 tsp per gl of RODI.
I’m checking potency with an HM Digital 100 using mS. I calibrated the mS with HM Digital solution.
I use the brs 1gl space saver and dose 480ml a day and still need to supplement 2 part.
I found this thread and have made 4 different 1gl solutions, starting from scratch on each. 1st, 2 tsp of brs kalk
2nd, 3 tsb of kalk
3rd, 4 tsb of kalk
4th, 6 tsb of kalk… all are under 7.14mS. Each jumps up about 1.0mS

I did 2 different batches of 1 cup RODI & 2 tsp of kalk, I just mixed differently. One by hand for 30sec or so and the 2nd on a magnetic stirrer for 20min. Magnetic stirrer was 7.12mS and the 30 sec hand mix was about 5.2

How do I achieve 10+mS or 12+ PH per gl?

 

[IonicBond]

I’ve got a question that I’m frustrated with.
I’m dosing kalk and doing 2 tsp per gl of RODI.
I’m checking potency with an HM Digital 100 using mS. I calibrated the mS with HM Digital solution.
I use the brs 1gl space saver and dose 480ml a day and still need to supplement 2 part.
I found this thread and have made 4 different 1gl solutions, starting from scratch on each. 1st, 2 tsp of brs kalk
2nd, 3 tsb of kalk
3rd, 4 tsb of kalk
4th, 6 tsb of kalk… all are under 7.14mS. Each jumps up about 1.0mS

I did 2 different batches of 1 cup RODI & 2 tsp of kalk, I just mixed differently. One by hand for 30sec or so and the 2nd on a magnetic stirrer for 20min. Magnetic stirrer was 7.12mS and the 30 sec hand mix was about 5.2

How do I achieve 10+mS or 12+ PH per gl?

How quickly are you testing these after mixing? If I'm reading corrrectly it is needing more time to saturate. I shake mine up vigorously in a gallon jug several times over about 12 hours, let it settle for about 12 hours, and get 10+ on Hanna DIST4 EC checker. I also add a little vinegar for posterity.