Calcium test kits

[Screwgunner]

I tested my water with hanna test kit said 390 salerfert 250. Imaginaqua 250. Why?

 

[Garf]

I tested my water with hanna test kit said 390 salerfert 250. Imaginaqua 250. Why?

I find the Salifert quite reliable. Are you adding 0.6ml of the test solution in one go, like it sais on the instructions? I haven't used the other two tests you mention.

 

[Screwgunner]

Well, I had to find out so I mixed 1 gallon of water with 1/2 cup salt I got .23 on the salt gravity so it should be 400 calcium. Hanna tested 504 salifert and the other one both tested 400 . That means my calcium has been 100 low .

 

[rishma]

I have long struggled with calcium test kits so I don’t test Ca anymore except the occasional ICP. I adjust everything off alkalinity tests and I dose calcium and alkalinity at the same time. A tank’s calcium consumption is reliably predicted off the alkalinity consumption. Been doing it this way for years since before I understood the ratios of alkalinity/calcium consumption. Turns out my aversion to Ca rest kits was well supported by science :)

 

[Miami Reef]

I bottled my tank water at the time of ICP testing with Oceamo, and I was able to “calibrate” my calcium Salifert tests. The kit itself was not accurate.

I’d rather just use a balanced dosing system and not worry about testing calcium or magnesium. An ICP once or twice a year is too easy.

 

[FernBluffReef]

I tested my water with hanna test kit said 390 salerfert 250. Imaginaqua 250. Why?

Make sure you are using vapor distilled water for the Hanna test and also rinsing the vials in distilled

 

[RabidDragon]

There are two primary reasons to obtain falsely elevated Ca results with the Hanna checker.

1. As FerBluffReef mentions, using anything other than Di water to test and rinse the testing vial/cap with after testing.
   1. This test kit is *very* sensitive and a single drop of dried tap water in the vail with give false elevated results.
2. The 100μL pipette has two stops when depressing the plunger, the first stop is where you depress it to drawing the water from your tank and into the pipette.... pushing the plunger to the second stop dispences all the tank water from the pippette and into your testing vial.
   1. When the water is drawn into the pipette tip, the water level should be right at the second line of the tip, if there is more water in the tip than this, you've over depressed the plunger.

Me: a scientist that performs lab tests daily.

 

[Randy Holmes-Farley Verified Community Expert]

1. This test kit is *very* sensitive and a single drop of dried tap water in the vail with give false elevated results.

The design of the Hanna calcium is poor for that reason, IMO. While I've not looked deeply into how else they could have done it, to use 100x as much DI water for the blank (10 mL) as the sample (0.1 mL) makes it hyper sensitive to small amounts of calcium in the blank. It is also going to be unusually sensitive to small changes in the sample volume, which at 0.1 ml is asking a lot. If they had somehow used 10 mL of blank and a new 10 mL of sample, both problems are significantly improved.

 

[fandaga]

I found my Ca testing precision with Hanna improved a lot when I switched from their syringe to an auto pipettor that I got off Amazon for $20. On Saturday my Hanna result was 453 and my Trident was 463. I also have the Salifert kit but prefer Hanna to verify my Trident.

Also, I use my RO/DI water. I haven’t found distilled necessary, but I could see that being an issue depending on your water quality. I guess you could try running a “blank” sample.

 

[RabidDragon]

removed and reposted.

 

[RabidDragon]

The design of the Hanna calcium is poor for that reason, IMO. While I've not looked deeply into how else they could have done it, to use 100x as much DI water for the blank (10 mL) as the sample (0.1 mL) makes it hyper sensitive to small amounts of calcium in the blank. It is also going to be unusually sensitive to small changes in the sample volume, which at 0.1 ml is asking a lot. If they had somehow used 10 mL of blank and a new 10 mL of sample, both problems are significantly improved.

Randy, we've reviewed this same topic in the past, and I do completely agree with you. With that being said, I'm sure that Hanna built the test around following:

• Being as similar in stepsconcept as possible to other tests in their catalog (using the 10ml vial and photometer)
• Reagents being as cheap possible while also easily available with stable availability.
• Reagents that are as minimally toxic as possible.

I don't doubt you could find a better test build... maybe you could patent it....
I have no problem obtaining consistant and accurate results with the system, but again this is what I do for a living. I beleive with a little guidance others can as well.

 

[awokenreefboy]

I tested my water with hanna test kit said 390 salerfert 250. Imaginaqua 250. Why?

I literally just went through this problem, but didn’t know where to post a PSA.

There are a few things that are tricky with the Hanna Calcium Checker. So here’s a few tricks I’ve picked up to ensure accuracy.

1. Make sure you clean everything with soap and water, and rinse out with RODI/Distilled water. While I haven’t really had to be so strict with other Hanna Checkers, the calcium one is super finicky and I’ve found to get accurate results you HAVE to clean them throughly after each use. Seems like common sense but I know I can get lazy.

2. You put reagent A into the vial first then fill with RODI water to the 10mL line which means you’re actually putting in 9mL of RODI water, not 10mL.

3. The 0.1mL micropipet is supposed to be pushed to the FIRST stop, put into water, draw sample, then pulled out of water. Many people will push it all the way down, THEN get their sample - this is wrong.

4. When you shake your sample and crystal reagent, make sure you do the same exact amount of time shaking every single time (15 seconds). And once done shaking, I like to gently swirl, and gently flick the vial to dissipate as many micro bubbles as possible (15 seconds).

Just like you I was getting readings 100+ compared to normal but after I did all these precautions I get accurate readings now.