high calcium levels cant be adjusted lower.

coralcruze · May 14, 2018

high calcium levels cant be adjusted lower.

For the longest time I cant seem to adjust my cal down... its reading 550 using red sea test kits that have been confirmed to be correct. in turn I have been trying to keep my alk at 11 dkh but guessing that because cal is so high forces my alk to drop over the course of a month. so I have been boosting my alk from 6 to 11 every month without any success.

mag is at 1400
po4 is .12
No3 is 5
temp is 78
sal 1.0025

I would like to keep alk at 10 and cal at 425. any suggestions on how to bring these levels down? I do use IO salt for water changes and also using a kalk reactor for top off.

Randy Holmes-Farley · May 14, 2018

The calcium at 550 ppm is not really keeping you from maintaining alkalinity, any more than a pH of 8.32 vs 8.20. Both have the same effect on precipitation of calcium carbonate.

Limewater (kalkwasser) will raise calcium long term, and may be part of the explanation, but water changes should easily correct it.

When you say IO salt, you mean normal Instant Ocean? Have you measured the calcium in it with your kit? It is likely below 400 ppm.

When you say you are boosting the alkalinity, how are you doing that?

RobZilla04 · May 14, 2018

What did you use to confirm the high Calcium test result? Another test kit, or simply another test with the same?

EliteReefing1023 · May 14, 2018

try changing your salt mix? io had high CA and changed my salt and it went away after a few WC

coralcruze · May 14, 2018

Hi Randy... yes regular IO but I boost the levels in that mix now for water changes... i use your two part formula to boost it..

I use two differant text kits by IO to determine alk and cal.

I didnt think kalk could raise calcium long term... i will consider doing a regular unboosted WC soon.

Randy Holmes-Farley · May 14, 2018

coralcruze said:
Hi Randy... yes regular IO but I boost the levels in that mix now for water changes... i use your two part formula to boost it..

I use two differant text kits by IO to determine alk and cal.

I didnt think kalk could raise calcium long term... i will consider doing a regular unboosted WC soon.

Yes, unboosted IO will work.

I used it for this very reason.

Happy reefing.

Randy Holmes-Farley · May 14, 2018

The reason limewater/kalkwasser raises calcium long term is that it provides calcium and alkalinity in the exact ratio present in calcium carbonate, but when calcium carbonate actually forms in a reef tank, magnesium and strontium get into the crystal in place of some of the calcium, so the demand for calcium is less than that in calcium carbonate (relative to alkalinity demand).

coralcruze · May 14, 2018

assuming no water changes... at what level would alk bring cal at 550 down? or would it?

Randy Holmes-Farley · May 14, 2018

coralcruze said:
assuming no water changes... at what level would alk bring 550 cal down? or would it?

It's not simple to say, but that level of calcium is not a big driver of precipitation. Some folks have oversimplified this issue to the point of being incorrect with analogies like a bowl full of marbles.

Even NSW at 420 ppm Ca/7 dKH and pH 8.2 is supersaturated with respect to calcium carbonate and some precipitation can occur. These sets of parameters have roughly equal chances of precipitation because pH is a BIG driver (it shifts bicarbonate into carbonate as pH rises):

Ca 420 ppm
Alk 7 dKH
pH 8.2

Ca 550 ppm
Alk 7 dKH
pH 8.08

coralcruze · May 14, 2018

Randy I use this calculator (http://reef.diesyst.com/flashcalc/flashcalc.html) when making corrections. is there a calculator which takes into account PH levels?

Randy Holmes-Farley · May 14, 2018

coralcruze said:
Randy I use this calculator (http://reef.diesyst.com/flashcalc/flashcalc.html) when making corrections. is there a calculator which takes into account PH levels?

pH does not impact the levels of alk or calcium, it just impacts the types of alk species present. Higher pH at fixed alkalinity means more carbonate and less bicarbonate. It is the carbonate concentration that really matters for precipitation, not the total alkalinity.

coralcruze · May 15, 2018

ok so I decided to experiment taking alk to 15 DKH and in a 24 hour period the Alk dropped back down to 12dkh and my PH was at 8.2 (low) - 8.53 (high) in thats same 24 hour period and Calcium is STILL at 550. I stopped dosing at 15 DKH because I started to see slight fogging of the water in the main display and I am not brave enough to continue

All corals are still happy and did not have the guts to go further.

So I have a question with all of this. I always understood Mg to slow down this effect. meaning I should not see Alk depletion so quickly, right? this is why I am confused with what is going on. I have not experienced this kind of chemical behavior in my tank. However i am SPS dominant with many corals growing nicely.

Randy Holmes-Farley · May 15, 2018

While magnesium slows precipitation, it won’t stop it, and raising the alk to 15 dKH and the pH to 8.5 is a recipe for greatly increased precipitation of calcium carbonate. It may also allow sps corals to grow faster if they have adequate nutrients. [emoji3]

coralcruze · May 15, 2018

Yes... po4 in particular is higher than normal at the moment and apparently a good thing under the circumstance.

Is it possible to get a heavily stocked sps reef to a pont where alk cal and mg stability is achieved?

Seems I am always chasing one of the params to stay put.