API Calcium test kit

[gwand]

I bought the API Calcium test kit to check calcium levels in my shrimp and Cray fish tank. Has anyone used this kit? The directions say the endpoint is when the tube turns a dark blue purplish color. I get a light blue color at around 60 ppm and if I continue to add drops of the solution, the test tube turns a slightly darker blue, but never the deep blue purplish color indicated in their instructions.

 

[Essjay]

The instructions on their website say to add 10 drops from bottle #1 then add drops from bottle #2 until the colour changes from pink to blue. As the test approaches the end point the pink turns purple, it should take just 1 or 2 more drops to turn blue.

If yours has gone blue, you've reached the end point. The colours on these testers only go darker when a lot of reagent has been added, ie when the level is high. When the level is low only a small amount of reagent is needed to reach the end point so it's pretty dilute and the colour pale. You can see the colour better if you remove the lid and stand the tube on something white and look down into the tube - now you are looking through a couple of inches of liquid rather than half an inch so the colour is intensified.
Since reef tanks have a calcium level of 400 to 500 ppm, they will be dark at the end point.


Incidentally, the calcium test is meant for reef tanks, I'm not sure how using it for fresh water would affect the colour changes. A GH tester meant for freshwater use will work just as well, if not better. GH is mainly calcium with some magnesium and trace amounts of other divalent metals.

 

[gwand]

The instructions on their website say to add 10 drops from bottle #1 then add drops from bottle #2 until the colour changes from pink to blue. As the test approaches the end point the pink turns purple, it should take just 1 or 2 more drops to turn blue.

If yours has gone blue, you've reached the end point. The colours on these testers only go darker when a lot of reagent has been added, ie when the level is high. When the level is low only a small amount of reagent is needed to reach the end point so it's pretty dilute and the colour pale. You can see the colour better if you remove the lid and stand the tube on something white and look down into the tube - now you are looking through a couple of inches of liquid rather than half an inch so the colour is intensified.
Since reef tanks have a calcium level of 400 to 500 ppm, they will be dark at the end point.


Incidentally, the calcium test is meant for reef tanks, I'm not sure how using it for fresh water would affect the colour changes. A GH tester meant for freshwater use will work just as well, if not better. GH is mainly calcium with some magnesium and trace amounts of other divalent metals.

Thanks. It must not work on fresh water tanks. Since the time of my post I used distilled water as a control and got the same results as with tank water with a GH 0f 180 ppm. Three drops of solution #2 following solution #1 and vial turns blue.

 

[Essjay]

3 drops = 60 ppm calcium according to the chart. This 60 ppm is not the same as GH in ppm. When GH is given as mg/l calcium carbonate (ie ppm) it means that's what the level would be if all the hardness minerals were calcium carbonate, which of course they aren't.
60 mg/l calcium = 150 ppm GH and 8.4 dH.

 

[gwand]

3 drops = 60 ppm calcium according to the chart. This 60 ppm is not the same as GH in ppm. When GH is given as mg/l calcium carbonate (ie ppm) it means that's what the level would be if all the hardness minerals were calcium carbonate, which of course they aren't.
60 mg/l calcium = 150 ppm GH and 8.4 dH.

Helpful. Thanks. But my point in my reply post was that the kit was indicating calcium levels of 60 ppm even when I used distilled water which has no minerals whatsoever. I am guessing the kit is not reliable in fresh water.

 

[Essjay]

Sorry, missed that point

It does sound as though that test needs salt water to develop the colours properly

 

[gwand]

Sorry, missed that point

It does sound as though that test needs salt water to develop the colours properly

I just emailed API to find out. I will keep you posted. Now for a follow up question. I thought the kit was accurate and when it indicated the shrimp tank calcium level was 60 ppm, I spiked the tank with calcium chloride to increase the calcium concentration. And of course the reading came back at 60 ppm so I added more calcium. Is it possible I added to much calcium and it could be toxic? I did a 40% water exchange just in case.

 

[Essjay]

Adding calcium will increase hardness. For fish we always say that changing any parameter by a large amount all at once is not good for them and I would treat shrimps the same way. So yes, the water change was a good idea, get it back to what it was and wait till you hear back from API - in my experience they do respond quickly although you may have to wait till Monday.

If API say it can't be used in fresh water I'd look at their GH/KH pair, and if you want to add calcium do it slowly.

For what it's worth I've had red cherry shrimps since 2013 and the colony is thriving. My water company says my GH is 140 ppm/7.95 dH. You don't need to go higher than that.

 

[MaloK]

I use the Fluval Ca test, It's for fresh and salt water, it contains 2 base and 1 reactant. No problem with readings.

 

[abandon_ship]

I just emailed API to find out. I will keep you posted. Now for a follow up question. I thought the kit was accurate and when it indicated the shrimp tank calcium level was 60 ppm, I spiked the tank with calcium chloride to increase the calcium concentration. And of course the reading came back at 60 ppm so I added more calcium. Is it possible I added to much calcium and it could be toxic? I did a 40% water exchange just in case.

Did API ever get back to you?

 

[gwand]

Did API ever get back to you?

No. They never responded.

 

[abandon_ship]

No. They never responded.

I'm going to get the "Monitor" brand low salinity ca/mg test from Amazon. Will report back.

 

[abandon_ship]

I'm going to get the "Monitor" brand low salinity ca/mg test from Amazon. Will report back.

API got back to me:

"The Calcium Test Kit is marketed for use with saltwater aquariums. So the instructions and indiations will all be for saltwater use.

However, the chemistry is a titration chemistry. This means that it will work on freshwater also. So the same 1 drop for every 20ppm calcium will still apply. We recommend to target at least 80ppm Calcium for invertibrates needing extra calcium, such as to build the shells of snails."

I wound up getting the "Monitor" low salinity ca/mg test anyways...