Test Kits

[daizeUK]

From your picture the 30 min test looks to me to be well above 1 ppm. And this points up the difficulty with all these tests, they are color based and human vision is not precise. That is why the more expensive and much more accurate lab grade tests do not rely on human eyes, instead they use a colorimeter to read the color.
 
But then there are the measurement issues. How certain is anybody that the drops coming out of the bottle are always uniform amounts? When one works with very small quantities and then imprecise measuring, results will always be questionable.

 
I agree, but my point in this thread was that you can't say that a test kit is 'accurate' until you have measured it against a known reference.  When I did this I proved that my API kit is NOT accurate.  I'd be interested if anybody wants to repeat a similar experiment with their API kit and prove whether API kits are generally inaccurate or whether I am unlucky enough to have a faulty kit!

 

[Ch4rlie]

I agree, but my point in this thread was that you can't say that a test kit is 'accurate' until you have measured it against a known reference.  When I did this I proved that my API kit is NOT accurate.  I'd be interested if anybody wants to repeat a similar experiment with their API kit and prove whether API kits are generally inaccurate or whether I am unlucky enough to have a faulty kit!

 
I'd like to try to an accuracy test on my API test kit, how do you do this?

 

[l_l_l]

Let me try repeating myself. Nitrate test kits are the least accurate in relation to these kits (listed in no particular order):
 
GH
KH
Nitrite
Ammonia
NH3
pH
 
I have used API kits for about 12 years. They can be used if one is aware of their short comings and inaccuracies. I have all of the above listed kits plus the nitrate kit. I have reordered them a couple of times as they have been used up or expired due to lack of use. I have not used a nitrate kit since setting up my high light co2 added planted tank about 12 years ago. I used the nitrate kit in that to see if i was getting 0 nitrates right before the water change. Once I knew it read 0 all the time, I knew i needed to add nitrate to my fertilizing regimen. Since then I have never used a nitrate kit.
 
Then there is the old Nitrate-nitrogen vs Nitrate (total ions). The way the hobby kits, including from API, work is they measure total ions. In science they use a different scale- the nitrogen scale. Think if it as measuring distance in miles vs kilometers and the nitrogen scale is miles while the total ion scales is like kilometers. Most times you see levels listed for being dangers to the fish in our tanks it originated using the nitrogen scale. But we are testing with the other scale. Here is the difference between the two.
 
1 ppm Ammonia- nitrogen = 1.28 ppm ammonia on the total ion scale.
1 ppm of Nitrite- nitrogen  = 3.28 ppm nitrite on the total ion scale.
1 ppm of Nitrate- nitrogen  = 4.42 ppm nitrate on the total ion scale.
 
Working with 10 ppm of Nitrate-nitrogen that would = about 45 ppm on an API kit. Note that 10 ppm of Nitrate-nitrogen is considered the safe limit for drinking water, even for infants, according to the 2002 US EPA guidelines. I believe they consider twice that (20 ppm as nitrogen) safe for most aquatic life for exposures less that 4 days.
 
Unless you are way overstocked and have no live plants, the odds pretty good are that doing weekly water changes of 35-50% will keep nitrates in a safe range. But out of curiosity, next time you test tank nitrates, test your tap levels at the same time- just prepare two vials and add the drops etc. to both and see what the results are.

Well I have in fact tested my water and aquarium water to determine the levels!
My tap water indicated 0 PPM, and aquarium, well.. Was about at 80 when I did it.
I'm pretty sure that when I first tested it, I was at 110 PPM, the water was home of way too many goldfish before and that was after a water change!
Doing a few water changes helped the issue, the nitrates were dropping accordingly to my water changes. In a 20% water change, 20% of the nitrates were going down..
Thats how I managed to "feel" my test kit.. But hey! I might be really wrong.
That's why I prefer having two test kits, and because I'm a bit of an Autist.

 

[pongo]

Thanks for the advice guys. By the looks of it everybody has their favorites. i will try a few and let you know in the near furture

 

[daizeUK]

I'd like to try to an accuracy test on my API test kit, how do you do this?

 
TTA gave an example of making your own reference solution by dissolving anhydrous ammonium salts in water in post #3 in this thread http/www.fishforums.net/index.php?/topic/415015-ammonia-testing-the-good-the-bad-and-the-ugly/.  I wouldn't go to that effort myself, to be honest.  I had a reference solution that came with my Seachem kit so I used that.
 
I was trying to think if it was possible to make a reference solution using Kleenoff or one of the other ammonium sources we tend to use for cycling, but I don't think it would be trustworthy because the ammonia will gas out of solution over time and you don't know exactly what concentration is left.  TTA might be able to advise better.