Salifert Calcium Test Problem - No Pink Color

[RobertK]

Calcium won’t change more than 25 ppm with a 3 dKH alk drop.

Yes but I stopped the calcium dosing for now too.

 

[Randy Holmes-Farley Verified Community Expert]

Yes but I stopped the calcium dosing for now too.

Exactly. So if alk drops 3 dKH, and you are not dosing more alk, calcium cannot drop more than 25 ppm.

I do not recommend alk dosing without calcium if you do not have a confirmed result that calcium is above your target range.

 

[RobertK]

Gotcha. Thanks Randy. I was not planning on dosing alk without Ca.

Adding a second syringe of titrant as you suggested did not help, as the test solution had already turned blue with the first syringe. It just kept getting bluer. Is diluting the test solution an alternative? Or just using 1 ml of tank water instead of 2? I did not get a clear endpoint with either of those techniques either so I remain puzzled.

Will try testing Ca again when alk is around 8, which is what I meant before.

 

[Randy Holmes-Farley Verified Community Expert]

Are these the approximate directions you are following?

Updated Instructions

1. Sample Preparation: Fill the test vial with 2 mL of aquarium water using the provided syringe.
2. Add Powder: Add 1 level scoop of Ca-1 powder reagent to the vial. Swirl gently for 5–10 seconds. Do not worry if not all powder dissolves.
3. Prepare Titrant: Attach the plastic tip to the 1 mL syringe. Draw 1 mL of Ca-2 (liquid reagent) into the syringe, ensuring the tip remains submerged and that the bottom of the black plunger sits exactly at the 1.00 mL mark.
4. Initial Addition: Add 0.6 mL of the Ca-2 reagent from the syringe into the test vial all at once.
5. Titration: Swirl the vial for 5 seconds. Continue adding Ca-2 reagent one drop at a time (from the same 1 mL syringe), swirling after each drop, until the solution changes from pink-red to a clear blue color.
6. Read Result: Hold the syringe with the tip upward and read the position of the bottom of the black plunger.
7. Calculate Calcium: Compare the remaining reagent amount (in mL) in the syringe to the table below:
   • 0.16 mL = 420 ppm
   • 0.14 mL = 430 ppm
   • 0.12 mL = 440 ppm
   • 0.10 mL = 450 ppm
   • 0.08 mL = 460 ppm

 

[RobertK]

Are these the approximate directions you are following?

Updated Instructions

1. Sample Preparation: Fill the test vial with 2 mL of aquarium water using the provided syringe.
2. Add Powder: Add 1 level scoop of Ca-1 powder reagent to the vial. Swirl gently for 5–10 seconds. Do not worry if not all powder dissolves.
3. Prepare Titrant: Attach the plastic tip to the 1 mL syringe. Draw 1 mL of Ca-2 (liquid reagent) into the syringe, ensuring the tip remains submerged and that the bottom of the black plunger sits exactly at the 1.00 mL mark.
4. Initial Addition: Add 0.6 mL of the Ca-2 reagent from the syringe into the test vial all at once.
5. Titration: Swirl the vial for 5 seconds. Continue adding Ca-2 reagent one drop at a time (from the same 1 mL syringe), swirling after each drop, until the solution changes from pink-red to a clear blue color.
6. Read Result: Hold the syringe with the tip upward and read the position of the bottom of the black plunger.
7. Calculate Calcium:Compare the remaining reagent amount (in mL) in the syringe to the table below:
   • 0.16 mL = 420 ppm
   • 0.14 mL = 430 ppm
   • 0.12 mL = 440 ppm
   • 0.10 mL = 450 ppm
   • 0.08 mL = 460 ppm

Yes. It normally turns pink after step 4 (and still does with fresh mixed saltwater) then turns blue during step 5. Mine has been turning blue (or a purplish color that is very hard to distinguish from blue) at step 4, so there is no clear endpoint during step 5.

 

[Randy Holmes-Farley Verified Community Expert]

Seems unlikely, but that is also consistent with very low calcium.

 

[RobertK]

Seems unlikely, but that is also consistent with very low calcium.

So it turns out my calcium level was low, around 335. Apparently my Salifert test won't read that low (or I can't detect a color change at that level). I've been using the Salifert calcium test kit for 15-20 years and never had a problem with it before.

I bought a Hanna calcium checker (I know its not your favorite Randy!) Watched a helpful video on how to use it correctly. I tested it out on newly mixed saltwater and got 447 with the Hanna and 440 with the Salifert, close enough. Checked the tank water twice with the Hanna and got readings of 334 and 336. Checked with Salifert, again just got a blue color and could not detect a color change from pink to blue. Assumed that the Hanna readings were accurate and added some CaCl to the tank to correct it. Rechecked afterward and got 398 with Hanna and 400 with Salifert (Salifert test now worked fine). Strange.

Not sure why my calcium was so low when my alk was too high. Will recalibrate my dosing pumps, maybe that was it. Thanks for the help Randy, maybe this will help someone else with a similar problem.

 

[Randy Holmes-Farley Verified Community Expert]

So it turns out my calcium level was low, around 335. Apparently my Salifert test won't read that low (or I can't detect a color change at that level). I've been using the Salifert calcium test kit for 15-20 years and never had a problem with it before.

I bought a Hanna calcium checker (I know its not your favorite Randy!) Watched a helpful video on how to use it correctly. I tested it out on newly mixed saltwater and got 447 with the Hanna and 440 with the Salifert, close enough. Checked the tank water twice with the Hanna and got readings of 334 and 336. Checked with Salifert, again just got a blue color and could not detect a color change from pink to blue. Assumed that the Hanna readings were accurate and added some CaCl to the tank to correct it. Rechecked afterward and got 398 with Hanna and 400 with Salifert (Salifert test now worked fine). Strange.

Not sure why my calcium was so low when my alk was too high. Will recalibrate my dosing pumps, maybe that was it. Thanks for the help Randy, maybe this will help someone else with a similar problem.

Yes, the current Salifert kit jumps past the endpoint even at the start if alk is low. It saves time and effort when calciumis normal, but causes issues with very low calcium. I think that makes it always pink, but whatever.

You're welcome and I'm glad its under control!

 

[RobertK]

the current Salifert kit jumps past the endpoint even at the start if alk is low

I think you mean if Ca is low? Alk was 7.5

 

[Randy Holmes-Farley Verified Community Expert]

I think you mean if Ca is low? Alk was 7.5

Oh, sorry, yes.