API kH Test

[Amy T]

When you are adding drops to the test tube for the API kH test do you count until exactly when the water turns from blue to yellow or when it turns BRIGHT yellow?  The instructions say "bright yellow" and it makes a big difference.

[Carl]

This is a good question.

I have always counted until it is clearly yellow, which may take one additional drop.

You could compare it to a KH dip strip for accuracy.
Personally for KH and GH, I prefer the dip strips, not because they are more accurate, but because neither are 100% accurate while at the same time both are "accurate enough" for general aquarium use and for me with my aquarium maintenance business, time was also important.

Resource:
www.americanaquariumproducts.com/Aquariumtestkit.html#5in1


You could also contact API for their opinion.


Carl

[devonjohnsgard]

My experience has been that it just takes one drop from yellow to bright yellow.

[angelminx]

I was never quite sure either, so what I do is:

Fill the test tubes with water (I test both my 55G and 10G at the same time so I can compare color differences on my test results--I've marked my test tubes for the 10G so I know which test is for which tank),

Then for GH and KH I add the approximate amount of drops (for example, if the last test result for KH was 4 drops, I add three drops), shake the tubes and look to see if there is any color change, then add one drop at a time from then on (if the color changes drastically with the 3 drops, since there may be an impending pH crash, I'll perform a 2nd test with 2 drops and see what happens). 

I compare the 2 at the same time against a white background.  If there is a "subtle" change in color, especially between the 2 test tubes, the comparison will tell me which one has a lower/higher color change.  For example, in one set of KH tests I recently performed, at 3 drops the 10G test tube barely showed a color change (a slight greenish tint) and the 55G turned green, so I added one more drop in each tube, and compared them again.  Compared to the 55Gs result (bright yellow--I have noted that there is no real color change when you add another drop of reagent to a sample that is already bright yellow), the 10Gs was a light yellow.  Since it would take less than one drop to make the change, I recorded the results as 3.5 degrees, and 4.25 degrees, respectively. 

I have had samples change directly from blue to bright yellow, but this doesn't happen as often as the  intermediate color changes.  My GH trends towards higher drop-counts, so when I test for it after a water change (my tap water averages ~8 drops) I always add about 5 drops less than the last reading, and then one drop at a time from there.  [Also, not all of my test tube caps fit as tightly as they should, and if I added one drop at a time from the very beginning, I would lose up to half the water I started with, making the readings incorrect--by adding the majority of drops to start with, I hardly lose any of the sample when I do lose any.]

I hope this helps.

Angelminx

[Carl]

Great suggestions Angelminx!!!

Carl

[Amy T]

Lol, Angelminx! I end up with a good bit of water on my hands for the gH test as well. Great advice! I will try your tactics next testing.

Thanks, everyone! I feel much clearer about reading the test:)

[angelminx]

I also hold a paper towel over the top of the test tube caps to help absorb any leaks while shaking.

[aguavida]

Angelminx! Oh my gosh! I do the very same thing! I caught on to this method soon after the first couple of times of testing when I had to count over 11 drops between shakes for KH and over 25 drops between shakes for GH due to my relatively high water hardness in my area so I can easily add (at the present moment) 20-25 drops right from the start to my GH test tube and add 1 drop between shakings from there, then also caught on to the paper towel idea for the same reason where the caps are not tight enough. As soon as I noticed there was residual solution on my hand I immediately went for the paper towel bc it also made me wonder how harmful all these test solutions might be and absorbing them through the skin is probably not a good idea especially if you're a health freak like me! 

[angelminx]

I haven't figured out why (especially when--I assume--these things are mass-produced) some of the lids fit more tightly on some tubes than others (is it the tube and/or the caps that are the loose-fitting culprits? ).  I have so many that I can't keep track to match the lids (to the tubes) that fit more snugly.  It seems like I can play "musical test tubes" with the caps and they fit each test tube differently...and then I can do the same with one test tube to the caps, and have different fits .  I now fill my test tubes (one tank at a time, with its designated tubes), then start fitting caps, and if the cap fits tightly, I place it in a different place or position than the other tubes--and use those for the GH/KH/Nitrate tests (in that order for me, depending on how many I find/which tests I'm doing).  I test both tanks together, so that I can perform the same test (for each tank) at the same time (this works out best for the timed tests, and comparing resulting colors ).  The GH test is the one that I use so many drops for, and since I can't buy the GH test separately, I don't test it that often.