View Full Version : api calcium test

01/15/2008, 08:05 AM
Can someone explain to me why the book has a purple endpoint picture but the instruction say the endpoint is blue?Also imo these api test result colors are way to close to each other to get an accurate reading.

01/15/2008, 08:11 AM
Same thing happens to me!!
I don't know where to stop adding drops. If it need to be really dark or only when it when from pink to purple it is enough!

01/15/2008, 08:50 AM
I have the same kit. I belive it is just a bad test kit. I can never get mine to match the end point color. I will add almost 20 drops and still no change. I would try a different kit. I also have the saltwater master test kit by them and i get inaccurate readings also.

01/15/2008, 08:59 AM
yea i'm getting a different kit asap.....

01/15/2008, 09:13 AM
I'll have to go back and double-check the instructions, but I thought it mentioned in there that you will see the color switch to purple right before it switches to blue. The color change is also VERY obvious - from pink, to purple, to blue, so no worries about missing the change. But it does help to know what the pink, purple, and blue colors look like.

My suggestion - don't go by the endpoint picture in the book. I just looked at the book and it looks purple to me!

My one complaint about the test though is the test tube. I think it is way too inconvenient to have to cap and mix the test tube after each drop of the titrating reagent, especially when it can take up to 20-25 drops to reach the endpoint. Although after awhile, you should know roughly where the endpoint should be, and just put a bunch of drops in at the beginning.

I think it would work much better if the test tube were wider, and you can just swirl with one hand, while dropping with the other hand. This is how the Chlorine test is for my pool, and works much better.

01/15/2008, 09:41 AM
I had no problems with this kit. The first time I was not sure if the color changed "enough" so I kept adding.

The second time I did it in natural light and it worked fine.

01/15/2008, 09:43 AM
Yea the endpoint picture in the book is as purple as purple gets!Not blue like the directions say.Mabey the whole research and development team was color blind.

01/15/2008, 10:15 PM
once it turns purple I usually add one more drop and thats as dark as it gets

I actually like the Ca API kit better than the salifert

01/15/2008, 10:39 PM
Mine turns purple, than with one more drop it changes to dark blue as well. Mine has a very obvious color change.

01/15/2008, 10:51 PM
Elos makes a great kit if you can find them, and they are not that expensive. Give em a try!

01/15/2008, 11:00 PM
I think the problem comes from being impatient and not adding the drops one at a time. I agree it's a PITA, but if you take your time and go one drop at a time (even if you know about where it should be) you see the change described (but not illustrated very well) in the book.

01/15/2008, 11:14 PM
as flakey as salifert has been lately I would choose anyone over them. As far as api goes, I really like the ca and their alk kit.

01/15/2008, 11:47 PM
There is a change from purple to blue. You have to keep adding drops until you get there.

01/16/2008, 12:57 AM
I don't have a problem with mine. You all need to realize that you must shake it well in between drops once you get to 9-10 drops. Providing that you have at least some traceable amounts of Calcium in your tank.
I know at minimum I usually have 350 which is around 13-15 drops I want to say. So I throw about 12 drops in there, shake well, then do one at a time shaking good in between each drop. It's really hard to mess up as the change is VERY obvious from the dark purple/pink color to dark blue.

arc eye
01/23/2008, 01:45 AM
I basically get only one color change around 17 to 18 drops. It goes from dark pink to purple/blue. I have tried adding a considerable amount of drops to get it a true blue, but feel they were merely wasted. It always seems to change around the same number of drops no matter how much Liquid reactor I had to the tank (granted liquid reactor probably isn't very effective).

I'm pretty skeptical and will definitely seek out alternatives. The fact that that they harp on hitting a blue end point yet show a purple end point color is ridiculous and only further obscures the accuracy of their product.

01/23/2008, 06:54 AM
I have had no problems with API as well. Salifert kit is cumbersom to use with adding spoon ful (which is never accurate!) of solid reagent followed by liquid reagent using a syringe! Also, you have to measure tank water with a syringe.

I used haggen in the begining but have since changed to API. I think I have had not problems with it. The endpoint transition is very clear. Purple color indicates the endpoint is REACHING and NOT the end point! one more drop and it turns blue which IS THE END POINT in titration. Also, I agree, their test tube is not very easy to use. So I use Haggens test tube (also marked with 5 mL line, use lower meniscus of water) which is wider and round at the bottom.

One way to tcheck if you have a correct end point, add two drops for your tank water to the tube AFTER you are done with test. It should go back to pink.

01/23/2008, 07:18 AM
I have had no problems with the API kit. I agree, user error is most likely the cause. Each drop is worth 20 calcium.

If you follow the instructions you will get a color change. You are looking for the color change and not a specific color, the drops themselves are purple so naturally droping purple liquid into clear liquid is going to result in pinkish purple liquid. There is an obvious color change. Per directions you can mix two drops at a time but you must shake well between the two drops. IMO if you hurry the kit along to fast, you will get inaccurate results and the color shift won't be as obvious. This is the same with any test kit, you have to follow the instructions.

Bad test kits happen, if you cannot get the kit to read right then you might have gotten a bad one, API will replace it. Each lot is tested many times over but im sure a few slip through.

01/23/2008, 07:32 AM
I add 20 drops before I shake it since I know I am always above 400. Comparing the results to my Saliftert ca test, if I go to blue, it reads higher. If I go to purple, it reads ~ the same., so I use the purple scale. I like the API ca and alk kits. Cheap and easy to use.

01/23/2008, 08:06 AM
The alk is great, might not give a solid number..... but 5 drops and shake, insta alk =]

The magnesium kit.. now there is a fun test to get figured out.

01/23/2008, 08:11 AM
<a href=showthread.php?s=&postid=11666752#post11666752 target=_blank>Originally posted</a> by tkeracer619
The alk is great, might not give a solid number..... but 5 drops and shake, insta alk =]

The magnesium kit.. now there is a fun test to get figured out.
Whos mag test?

01/23/2008, 08:45 AM
I absolutely love the API test kit, and would recommend it to anyone. The endpoint isn't so much a change to true-blue as much as it's a change to very dark purple/blue. Either way, it's very obvious with my kit. If you're not getting a very noticable change in color, then keep adding drops. Mine doesn't change until drop 22-24.

Also, to the person who said it's annoying to have to cap the test tube and shake after every drop: just put your finger over it. I can run the entire test in ~30 seconds. Since my Ca is always >400ppm, I put in 20 drops instantly, shake real good, then add dropwise and shake with my finger over the top. Just a recommendation!

01/23/2008, 09:05 AM
<a href=showthread.php?s=&postid=11666784#post11666784 target=_blank>Originally posted</a> by sjm817
Whos mag test?

Sorry I just pulled out my box-o-bottles and the mag test kit I was referring to is actually a red sea and not API. I have quiet a few kits and have almost lost track of what brand is what at 5-6 in the morning ;)

The kit itself isn't hard to do, its just that you should run through it a few times to get the hang of it or else you get to the halfway point and say "huh I do what......" then mess up the actual test :D

Most test kits are reliable enough for hobbiest purposes if the hobbiest is reliable enough for the test kit. I had a funky alk bottle that ended up having a bad nipple, swapped it with the top of an old empty bottle and the test kit was right back on where it was supposed to be.