Can't measure Calcium in DT.

[Stelioshah]

So, here's the thing. I have been only dosing NaHCO3 for a couple of years already. Lately a montipora digitata frag that I have has taken off and is growing rapidly. I was thinking to switch to Ca(OH)2 dosing. I used to measure Mg and Ca in the past but I stoppped as I found no real reason to do so until now. I ordered a salifert Calcium test kit. If you are not familiar with the test kit you need to add 2mLs of water, then a scoup of the powder and before mixing you need to add 0.6mLs of the titration solution. The color of the liquid should now be pink, by continuing the titration, you should reach the final blue color. I did this multiple times and no matter what I do (no matter how much titration solution I add in the second step, no matter the order of the steps taken, no matter how much of the titration solution I add in total) the solution NEVER gets a pink color, it instantly goes to blue, from the very first drops of the titration solution. This should Indicate that my Ca is 0, which seems highly unlikely to me as I do not have even a single stressed coral currently.

In the mean time the test kit WORKS CORRECTLY on my freshly mixed saltwater per my salt's expected Ca2+ concentration. I will be doing a waterchange shortly. I was contemplating whether Mg was interrupting the titration as I have a high concentration of Mg (~1500ppm), but my mixed salt water has the same concentration... pH is ~8.15 and alkalinity is 8.5dkh. Any ideas?

 

[Randy Holmes-Farley]

It means the calcium level is below the amount of titrant added instantly (which I think corresponds to 300 ppm). There are several ways to get an answer from it, such as using a 50/50 mix of tank water and new salt water, and back calculating the value.

For now, however, I'd add 25 ppm of calcium per day until you get a reading.

 

[braaap]

So, here's the thing. I have been only dosing NaHCO3 for a couple of years already. Lately a montipora digitata frag that I have has taken off and is growing rapidly. I was thinking to switch to Ca(OH)2 dosing. I used to measure Mg and Ca in the past but I stoppped as I found no real reason to do so until now. I ordered a salifert Calcium test kit. If you are not familiar with the test kit you need to add 2mLs of water, then a scoup of the power and before mixing you need to add 0.6mLs of the titration solution. The color of the liquid should now be pink, by continuing the titration, you should reach the final blue color. I did this multiple times and no matter what I do (no matter how much titration solution I add in the second step, no matter the order of the steps taken, no matter how much of the titration solution I add in total) the solution NEVER gets a pink color, it instantly goes to blue, from the very first drops of the titration solution. This should Indicate that my Ca is 0, which seems highly unlikely to me as I do not have even a single stressed coral currently.

In the mean time the test kit WORKS CORRECTLY on my freshly mixed saltwater per my salt's expected Ca2+ concentration. I will be doing a waterchange shortly. I was contemplating whether Mg was interrupting the titration as I have a high concentration of Mg (~1500ppm), but my mixed salt water has the same concentration... pH is ~8.15 and alkalinity is 8.5dkh. Any ideas?

So to me that would mean your calcium is somewhere around 300. Because right off the bat you are adding .6 of the solution. .4 remaining is 300ppm

 

[Stelioshah]

It means the calcium level is below the amount of titrant added instantly (which I think corresponds to 300 ppm). There are several ways to get an answer from it, such as using a 50/50 mix of tank water and new salt water, and back calculating the value.

For now, however, I'd add 25 ppm of calcium per day until you get a reading.

I already tried this. I tried 1mL aquarium water and 1mL mixed saltwater and also 0.5mLs aquarium water with 1.5mLs mixed water. I got nothing in the first test, instantly blue again, and with the second test I got calcium out of chart. I also tried to not add the 0.6mls instantly and add drop wise from the very beginning. It still went to blue instantly.

 

[Stelioshah]

I am doing a water change right now, I will inform back later

 

[Randy Holmes-Farley]

I'd just go with the dosing.

 

[Stelioshah]

I will measure again in a few hours. I don't know what the frick is going on. I did a ~50% water change. I tried to measure again and after adding the 0.6mLs the solution was still blue, I kept adding and it turned pink at the 0.8mL mark. In the end I measured 500ppm Ca.

 

[Stelioshah]

My salinity is on point.

 

[Randy Holmes-Farley]

What salt mix are you using? What was its calcium level?

 

[Stelioshah]

What salt mix are you using? What was its calcium level?

Something is off about the test. I measured my mixed saltwater 3 more times and they all measured at around 600-650ppm (added 1.2-1.3mLs). if you extend the graph. I have an almost empty old test which measures 450ppm. Tropic marine pro reef.

 

[Randy Holmes-Farley]

Something is off about the test. I measured my mixed saltwater 3 more times and they all measured at around 600-650ppm (added 1.2-1.3mLs). if you extend the graph. I have an almost empty old test which measures 450ppm. Tropic marine pro reef.

Be sure you are not reading the table backwards. Many people do that.

 

[Stelioshah]

With my old test, after measuring the aquarium 0.1mLs remained so it measured 450ppm again... I don't think I will manage to make the switch to Ca(OH)2 with this new test

 

[Randy Holmes-Farley]

With my old test, after measuring the aquarium 0.1mLs remained so it measured 450ppm again... I don't think I will manage to make the switch to Ca(OH)2 with this new test

Calcium hydroxide should be dosed to maintain alk. If you do, it is maintaining calcium wherever it is. If calcium is too low, correct it upwards with calcium chloride, and if it is too high (say, above 550 ppm or so), water changes are the only way to lower it.