How to mitigate rising Ca when dosing Kalk?

Jonify · Jan 6, 2021

Posting this in the SPS forum, too, because that's what I'm targeting.

Question is, when dosing Kalk, you typically have Ca increases disproportionate to alkalinity (albeit very slowly) since kalk is not a truly balanced additive. How do successful reefers overcome this? Are water changes enough? Do you mix saltwater with lower calcium (so 34 ppt with most mixes) and then dose up alkalinity/Mg? Do you alter the kalk solution? I'm not using kalk (anymore), but I'm considering dosing it very slowly overnight, mostly to help with the diurnal swing--which is a pretty fantastic use of kalk, if normal daylight alk and pH ranges are good, but also to eek out a little more runway from my ATO (I have a 20G nano, and am not willing to hook my RO up to the ATO, so that's a no-go--trying to focus this on the specific Kalk question

)

Nano sapiens · Jan 6, 2021

When I want to reduce the calcium level, I just stop using Kalkwasser and substitute an alkalinity only product (I use Seachem Reef Builder) to continue maintaining stable alkalinity. Once the calcium level has dropped to 410 ppm or so, I return to using Kalkwasser again and repeat the process whenever calcium gets too high.

Randy Holmes-Farley · Jan 6, 2021

In my case, i did my regular water changes with a lower calcium mix: normal IO. That kept it perfect for the very long term.

Using a little baking soda for an occasional alk boost will also do the trick.

Randy Holmes-Farley · Jan 6, 2021

Here's my comment from my Triton ICP article:

Calcium (Ca). In my reef aquarium, I use only Instant Ocean salt and I have not added any additional calcium except as limewater for a number of years (during which time I have continued regular 1% daily water changes). So why is my calcium level (472 mg/L) higher than one would normally expect for Instant Ocean (maybe between 350 and 400 mg/L)? That long term rise in calcium is actually the expected result when using limewater to maintain alkalinity.

Limewater adds calcium and alkalinity in exactly the same proportions as in pure calcium carbonate. So if that is what is used by corals to make skeletons, and what precipitates on pumps and such, then calcium would stay constant.

But both magnesium and strontium get into growing calcium carbonate crystals in place of some of the calcium. A few percent of the calcium is replaced this way. Consequently, since the same amount of alkalinity (the carbonate) is used over time, and somewhat less than the balancing amount of calcium, calcium rises if alkalinity is maintained. I’m happy to see the result match the theory, and the calcium level seems fine to me.

My Triton Testing Results: By Randy Holmes-Farley - REEFEDITION

Recently, Triton GmbH in Germany has initiated a method of testing many ions at once for a single price. In the US, that service is coordinated by Unique Corals. For $49 they will send you a couple of tubes to collect a tank water sample, and a prepaid mailer to send the sample back to them...

www.reefedition.com

Jonify · Jan 6, 2021

Nano sapiens said:
When I want to reduce the calcium level, I just stop using Kalkwasser and substitute an alkalinity only product (I use Seachem Reef Builder) to continue maintaining stable alkalinity. Once the calcium level has dropped to 410 ppm or so, I return to using Kalkwasser again and repeat the process whenever calcium gets too high.

Randy Holmes-Farley said:
In my case, i did my regular water changes with a lower calcium mix: normal IO. That kept it perfect for the very long term.

Using a little baking soda for an occasional alk boost will also do the trick.

Oh perfect. Exactly what I was looking for--thank you!

Jonify · Jan 6, 2021

Randy Holmes-Farley said:
Here's my comment from my Triton ICP article:

Oh nice--thanks for sharing that ... good read and I'm bookmarking to go back and read it again. The point on strontium is interesting.

ReefBeta · Jan 24, 2021

Randy Holmes-Farley said:
Here's my comment from my Triton ICP article:

Calcium (Ca). In my reef aquarium, I use only Instant Ocean salt and I have not added any additional calcium except as limewater for a number of years (during which time I have continued regular 1% daily water changes). So why is my calcium level (472 mg/L) higher than one would normally expect for Instant Ocean (maybe between 350 and 400 mg/L)? That long term rise in calcium is actually the expected result when using limewater to maintain alkalinity.

Limewater adds calcium and alkalinity in exactly the same proportions as in pure calcium carbonate. So if that is what is used by corals to make skeletons, and what precipitates on pumps and such, then calcium would stay constant.

But both magnesium and strontium get into growing calcium carbonate crystals in place of some of the calcium. A few percent of the calcium is replaced this way. Consequently, since the same amount of alkalinity (the carbonate) is used over time, and somewhat less than the balancing amount of calcium, calcium rises if alkalinity is maintained. I’m happy to see the result match the theory, and the calcium level seems fine to me.

My Triton Testing Results: By Randy Holmes-Farley - REEFEDITION

Recently, Triton GmbH in Germany has initiated a method of testing many ions at once for a single price. In the US, that service is coordinated by Unique Corals. For $49 they will send you a couple of tubes to collect a tank water sample, and a prepaid mailer to send the sample back to them...

www.reefedition.com

But many people are dosing 2 parts in equal amount without seeing much raise in calcium, me included on my old build. That has the same alk to ca ratio as kalk, but why only kalk causing ca to raise?

Randy Holmes-Farley · Jan 24, 2021

ReefBeta said:
But many people are dosing 2 parts in equal amount without seeing much raise in calcium, me included on my old build. That has the same alk to ca ratio as kalk, but why only kalk causing ca to raise?

That's a good question. They do not necessarily have the same ratio.

My DIY (e.g., BRS recipe) contains 37,000 ppm calcium and 5300 dKH alkalinity, for a ratio of 19.5 ppm calcium for each 2.8 dKH (1 meq/L) of alkalinity while limewater contains 20 ppm calcium for each 2.8 dkh of alkalinity.

Moreover, I speculate that no one using a two part can dose exactly 1:1 for a long period without drifting from that ratio and making occasional corrections. You'd need to regularly make fairly accurate volume measurements, and most people that are dosing do not measure the dose so accurately. The difference between 19.5 mL and 20 mL would swamp the effect.

ReefBeta · Jan 24, 2021

Randy Holmes-Farley said:
That's a good question. They do not necessarily have the same ratio.

My DIY (e.g., BRS recipe) contains 37,000 ppm calcium and 5300 dKH alkalinity, for a ratio of 19.5 ppm calcium for each 2.8 dKH (1 meq/L) of alkalinity while limewater contains 20 ppm calcium for each 2.8 dkh of alkalinity.

Moreover, I speculate that no one using a two part can dose exactly 1:1 for a long period without drifting from that ratio and making occasional corrections. You'd need to regularly make fairly accurate volume measurements, and most people that are dosing do not measure the dose so accurately. The difference between 19.5 mL and 20 mL would swamp the effect.

Ah, I was not realized the difference in ratio on 2 parts formula. That make lots of sense. I'm also wondering about calcium reactor then. If it's using old coral skeleton as media, it would be fine. But there are many other media that are not coral skeleton and they just magically have the same ratio of the actual usage by coral? I'm just a bit surprised that's not a more commonly raised question.

Randy Holmes-Farley · Jan 24, 2021

ReefBeta said:
Ah, I was not realized the difference in ratio on 2 parts formula. That make lots of sense. I'm also wondering about calcium reactor then. If it's using old coral skeleton as media, it would be fine. But there are many other media that are not coral skeleton and they just magically have the same ratio of the actual usage by coral? I'm just a bit surprised that's not a more commonly raised question.

Yes, with a reactor you are stuck with a ratio that may vary with the media.

Kris4647 · Feb 11, 2021

Randy Holmes-Farley said:
That's a good question. They do not necessarily have the same ratio.

My DIY (e.g., BRS recipe) contains 37,000 ppm calcium and 5300 dKH alkalinity, for a ratio of 19.5 ppm calcium for each 2.8 dKH (1 meq/L) of alkalinity while limewater contains 20 ppm calcium for each 2.8 dkh of alkalinity.

Moreover, I speculate that no one using a two part can dose exactly 1:1 for a long period without drifting from that ratio and making occasional corrections. You'd need to regularly make fairly accurate volume measurements, and most people that are dosing do not measure the dose so accurately. The difference between 19.5 mL and 20 mL would swamp the effect.

Evening Randy, I definitely found a few after action items here. Would you consider high calcium an emergent situation or adverse to coral growth calcification?

I’ve been sitting at 620, 8.5 meq (trident) for a week or so after a water change with Tropic Marin. Alkalinity is tracking but the Ca is stuck.

Planning a water change with IO

Thanks for your time!

Randy Holmes-Farley · Feb 12, 2021

I do not know for certain, but I expect few biological problems at elevated calcium.

The biggest risk is more abiotic precipitation of calcium carbonate.

Derrick0580 · Jul 10, 2022

Randy Holmes-Farley said:
Here's my comment from my Triton ICP article:

Calcium (Ca). In my reef aquarium, I use only Instant Ocean salt and I have not added any additional calcium except as limewater for a number of years (during which time I have continued regular 1% daily water changes). So why is my calcium level (472 mg/L) higher than one would normally expect for Instant Ocean (maybe between 350 and 400 mg/L)? That long term rise in calcium is actually the expected result when using limewater to maintain alkalinity.

Limewater adds calcium and alkalinity in exactly the same proportions as in pure calcium carbonate. So if that is what is used by corals to make skeletons, and what precipitates on pumps and such, then calcium would stay constant.

But both magnesium and strontium get into growing calcium carbonate crystals in place of some of the calcium. A few percent of the calcium is replaced this way. Consequently, since the same amount of alkalinity (the carbonate) is used over time, and somewhat less than the balancing amount of calcium, calcium rises if alkalinity is maintained. I’m happy to see the result match the theory, and the calcium level seems fine to me.

My Triton Testing Results: By Randy Holmes-Farley - REEFEDITION

Recently, Triton GmbH in Germany has initiated a method of testing many ions at once for a single price. In the US, that service is coordinated by Unique Corals. For $49 they will send you a couple of tubes to collect a tank water sample, and a prepaid mailer to send the sample back to them...

www.reefedition.com

I am currently experiencing this exact issue. Tonights testing yielded these results:

PH 7.94 (pinpoint probe)
Nitrate 0.0 (not good, cut fuge light back 2 hrs)
Phosphate 0.07
Ammonia 0
Nitrite 0
Alkalinity 8.3
Magnesium 1460 (aqua forest kit)
Calcium 500 (red sea pro kit)

I dose kalkwasser from midnight till noon while tank lights are off only 450ml, and then only 50ml through out the rest of the day as the versa will not allow me to dose nothing during the day and only dose at night so I must dose something during the day time. Should I just be checking alk and cal every few days until calcium drops down to normal and kick the kalk back on as I have turned the pump off for now.

Randy Holmes-Farley · Jul 10, 2022

There’s nothing wrong with 500 ppm calcium, and I’d personally stay the course, with some additional alk supplement to offset additional calcium rise.