Salifert Calcium Test

[Salt It Away]

Has anyone else had an issue with the Ca-2 solution dropper bottle? Getting 8 uniform drops from that bottle has become a real chore. Tried every method from bleeding first drop to relieving pressure after each drop. Getting dribble or double drops every time.

 

[jd371]

I had the same issue, I now use an eye dropper.

 

[Wilsoni]

+2 it's a pain

 

[sc50964]

I have been using API for Ca for the past 10 years. It's easy and affordable.

 

[Salt It Away]

I have been using API for Ca for the past 10 years. It's easy and affordable.

Unfortunately, I don't trust API anything.

 

[Randy Holmes-Farley Verified Community Expert]

Has anyone else had an issue with the Ca-2 solution dropper bottle? Getting 8 uniform drops from that bottle has become a real chore. Tried every method from bleeding first drop to relieving pressure after each drop. Getting dribble or double drops every time.

The result is not likely dependent on the exact amount added, so I wouldn't agonize over this step. It is only the tank sample and the titration volume that are critical measurements (I believe, perhaps Habib will correct if wrong).

 

[sc50964]

Unfortunately, I don't trust API anything.

IMO, regardless what brand of testing kit, I would always do a sample test based on a known water source. All brands have errors in their batch production from time to time. Hanna just recently had some major issues after long being a model of perfection. I use API coz I keep mostly LPS and it offers enough accuracy (lowest domination is 10s I believe).

 

[Salt It Away]

IMO, regardless what brand of testing kit, I would always do a sample test based on a known water source. All brands have errors in their batch production from time to time. Hanna just recently had some major issues after long being a model of perfection. I use API coz I keep mostly LPS and it offers enough accuracy (lowest domination is 10s I believe).

I respect your position.

 

[Pete polyp]

I had an issue with salifert giving me false readings. Even with a brand new kit it was giving false readings. I bought an api and elos kit and the readings were the exact same. I threw the salifert in the trash and never used it again.

 

[sc50964]

When in doubt, just take a water sample to your LFS

 

[KingBlingTX]

The result is not likely dependent on the exact amount added, so I wouldn't agonize over this step. It is only the tank sample and the titration volume that are critical measurements (I believe, perhaps Habib will correct if wrong).

I was wondering about this since I have experienced the same issue with Ca-2 solution! I assumed it must be an excess reagent since it is not precisely measured.

 

[Salt It Away]

I was wondering about this since I have experienced the same issue with Ca-2 solution! I assumed it must be an excess reagent since it is not precisely measured.

Well, not to beat a dead seahorse, but when instructions say "8" drops, I assume there is cause for that. If the instructions said "Approximately 8 drops" I never would have brought it up.

 

[Habib(Salifert)]

The result is not likely dependent on the exact amount added, so I wouldn't agonize over this step. It is only the tank sample and the titration volume that are critical measurements (I believe, perhaps Habib will correct if wrong).

The short answer is what Randy said.

For an extra ease of mind I will give more in details in a couple of hours.

 

[Habib(Salifert)]

The exact amount of Ca-2 reagent is not critical as long as a certain minimum amount is added, the minimum amount is far less than 8 drops. Hence the dropsize is not critical or important.

Please try it in the following way, which deviates slightly from the instructions, to see if it goes ok and for ease of mind

Add 2 ml of aquarium water to the test vial.

Add one (approx. Level) scoop of Ca-1 powder and swirl for a few seconds. The color will very likely be blue.


Add drop by drop of the Ca-2 reagent and swirl one or two seconds after each drop. By approx. 4 or 5 drops it should be red/pink.

Add 3 or 4 more drops after it has become red/pink.

You can now proceed with the Ca-3 part as in the instructions.
Allmost all of the drops added of the Ca-2 after it goes pink is excess.
Once you see that you achieve that at approx. 4 or 5 drops you should feel comfortable that when adding 8 drops not all drops are the same size and that it doesn't matter.

 

[JimWelsh]

It wouldn't hurt for people to actually understand what is really happening with test kits, to avoid stress, anxiety and confusion regarding them. Virtually all calcium test kits on the market are doing the same basic analysis: An EDTA titration of calcium, using an indicator dye, after first precipitating magnesium as the hydroxide.

What did Jim just say? Was that English?

EDTA is a big molecule that likes to grab onto metal ions, like calcium, magnesium, strontium, and so on. There are various indicator dye molecules that also like to grab onto these metal ions. The "strength" with which EDTA grabs the metal ions is stronger than the "strength" of the dyes, so EDTA will strip the metal ions away from the dye molecules. The dye molecules are one color when they have metal ions attached (pink), and change color (to blue) when they are "naked", or when the EDTA has grabbed all the metal ions. This is the classic "pink to purple to blue" color change. By measuring the amount of EDTA it takes to gobble up all the metal ions to the point where it causes the color change, we can know the amount (in "moles") of metal ions that were in the water.

To get just calcium results, we have to do something about all that magnesium in the water. The classic solution to this problem exploits the fact that magnesium hydroxide is extremely insoluble in water, and so either sodium or potassium hydroxide is added, which almost immediately causes the cloudy white precipitate that is magnesium hydroxide. The magnesium "grabs" onto the hydroxide so strongly that neither the dye nor the EDTA can get ahold of it, and so it is just like it wasn't there. Another thing the hydroxide does is to get the pH of the solution in the right range for the dye to do it's color change thing properly.

How much hydroxide is necessary? Enough to get the job done, but adding too much won't hurt anything. Adding too little will leave some magnesium in solution, and will cause the test to read high.

As far as the amount of dye necessary, you really only need enough to see the color well enough to detect the color change. Adding too little or too much dye doesn't really hurt anything, either.

Measuring the amount of EDTA titrant accurately is the one really important part of the calcium test.

EDIT: One minor note: Any strontium in the water is still present, and acts just like calcium in these titrations, so most calcium test kits actually are calcium + strontium test kits. Remember I said that we are measuring moles of metal ions. Strontium weighs about twice what calcium does, so that means that 8PPM strontium in your water would mean a 4PPM error in the calcium reading. Some test kit manufacturers may attempt to factor this error into the results calculation by guessing how much strontium you might have in your tank, and others likely just ignore this error. In any event, the error is likely very small, but I just wanted to mention it.

 

[Salt It Away]

The exact amount of Ca-2 reagent is not critical as long as a certain minimum amount is added, the minimum amount is far less than 8 drops. Hence the dropsize is not critical or important.

Please try it in the following way, which deviates slightly from the instructions, to see if it goes ok and for ease of mind

Add 2 ml of aquarium water to the test vial.

Add one (approx. Level) scoop of Ca-1 powder and swirl for a few seconds. The color will very likely be blue.


Add drop by drop of the Ca-2 reagent and swirl one or two seconds after each drop. By approx. 4 or 5 drops it should be red/pink.

Add 3 or 4 more drops after it has become red/pink.

You can now proceed with the Ca-3 part as in the instructions.
Allmost all of the drops added of the Ca-2 after it goes pink is excess.
Once you see that you achieve that at approx. 4 or 5 drops you should feel comfortable that when adding 8 drops not all drops are the same size and that it doesn't matter.

Thanks Habib. That does make sense and quite frankly makes me feel like I know what the procedure is designed to do. Thanks for taking the time to explain.