Reef Chemistry Question of the Day #210 Limewater/Kalkwasser Long Term Use

Randy Holmes-Farley · Sep 6, 2017

Orm Embar said:
Randy - thanks for the explanation! How do you deal with the rising calcium? Just use alkalinity replacement and wait for the calcium to naturally drop, rely on partial water changes to maintain an equilibrium, or something else?

I changes 1% daily with a lower calcium mix, normal Instant Ocean. Here's my comment after a Triton test:

http://www.reefedition.com/my-triton-testing-results-by-randy-holmes-farley/

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.

Mike.kel · Sep 6, 2017

So if Magnesium drops so does strontium and all other traces elements?

Is there a way to calculate a ball park amount of drop in those other elements using Lime Water similarly to how RedSea coral colors are added based on the amount of their calcium additive?

My tank uses @$30 in Lime a year so I'm hooked on the method. I also like instant ocean.

Randy Holmes-Farley · Sep 6, 2017

Mike.kel said:
So if Magnesium drops so does strontium and all other traces elements?

Is there a way to calculate a ball park amount of drop in those other elements using Lime Water similarly to how RedSea coral colors are added based on the amount of their calcium additive?

My tank uses @$30 in Lime a year so I'm hooked on the method. I also like instant ocean.

No, there's no good way to predict the demand for trace elements, and they are certainly not tightly related to calcium and alkalinity consumption since in many tanks, the primary users are soft corals and algae of various types.. Red Sea just picked values that seems to work, but luckily, the exact trace element concentrations seem not very important. In fact, Red Sea recommends iron levels that are way, way higher than natural sea surface levels (recommended 0.15 ppm iron, natural levels more like 0.000006 ppm in many settings).

Mike.kel · Sep 6, 2017

That's interesting to know about that particular kit. I am definitely going to be trying the ICP testing soon to see just where I need to improve my tanks chemistry to be more or less balanced with NSW. Thank you for sharing your knowledge Doc!

Randy Holmes-Farley · Sep 6, 2017

You're welcome.

Happy Reefing.

Akutila · Sep 7, 2017

Thanks for this information Randy! This answered the question that's been buggering my head about constantly high calcium level in my tank with only limewater dosing.

And that raises a follow up question: Does it have harmful effects on the tank if you boost up the alkalinity with sodium carbonate but don't add any calcium chloride or add it less than sodium carbonate? Does it mess up the balance when you add more sodium than chloride ions and should I be worried in long term?

Randy Holmes-Farley · Sep 7, 2017

Those sorts of occasional corrections with just sodium carbonate or bicarbonate are fine.

Hethari · Nov 18, 2017

I have another question if i use lime water longtime does that affect salinity on long term as no sodium or chloride is added unlike two part dosing

Sabellafella · Nov 18, 2017

Hethari said:
I have another question if i use lime water longtime does that affect salinity on long term as no sodium or chloride is added unlike two part dosing

Well if your dosing more then your typical evaporation then sure it would alter your sg.

Randy Holmes-Farley · Nov 18, 2017

Hethari said:
I have another question if i use lime water longtime does that affect salinity on long term as no sodium or chloride is added unlike two part dosing

It has no significant impact on salinity over time (unless you add more liquid than evaporates, as noted above).

MnFish1 · Nov 18, 2017

Randy Holmes-Farley said:
A. Calcium will slowly rise
B. Calcium will slowly fall
C. Magnesium will slowly rise
D. Magnesium will slowly fall
E. The true carbonate alkalinity will slowly decline as it is replaced by hydroxide alkalinity
F. The true carbonate alkalinity remains unchanged but the total alkalinity increases due to accumulation of hydroxide

Im saying D
B, C and E do not make sense
F isn't true because hydroxide alkalinity does not accumulate.

About A -- Doesn't A depend on the amount of calcium uptake by whatever is in the tank? - I guess if the alk is maintained, the Ca won't increase 'much if at all' so Ill stick with D.

EDIT - why do i always see these questions after they are answered lol

Hethari · Jan 10, 2018

Hello randy
What’s your opinion on adding vinegar to kalkwasser

Randy Holmes-Farley · Jan 10, 2018

Hethari said:
Hello randy
What’s your opinion on adding vinegar to kalkwasser

If you need a little more potency than saturated limewater can give you, it can be a reasonable way to go.

As a way to deliver organic carbon, it is also OK, but I preferred to dose them separately (and did dose both at the same time but separately) so that I could control the timing of the dosing of the vinegar better (I wanted to dose during the daylight when O2 and pH were highest, since it reduces both).