Aquarium Coop test strips versus API master kit

[GreenCircleGirl]

I find testing nitrates really frustrating.  For the API master kit, my nitrate reading is always red….which means it is 40 or more…..????  I can’t tell the difference between 40 and 100 with the master kit.  With other test strips, I have the same problem. I can’t differentiate the pinks to tell what the reading actually is.  I CAN actually differentiate the pinks on the Aquarium Coop strips which is so helpful. BUT….the Aquarium Coop strips read 25 ish but testing the same water with API master kit shows dark red which means over 40.  I want to  shoot for changing the water when the nitrates are 50 ish.  I’m trying to feel comfortable about doing fewer water changes and allowing the nitrates to be a bit higher for the plants, but I’m frustrated because I don’t know what to trust. How can things be so incongruent?

[nabokovfan87]

On 7/10/2022 at 2:40 PM, GreenCircleGirl said:

 I want to  shoot for changing the water when the nitrates are 50 ish.  I’m trying to feel comfortable about doing fewer water changes and allowing the nitrates to be a bit higher for the plants, but I’m frustrated because I don’t know what to trust. How can things be so incongruent?

I would encourage you to try to keep nitrates lower than 40, preferably below 20.   I used to shoot for 40's and had severe issues with algae as a result (among other reasons).

May I ask what is in the tank in question and if you have plants in the tank?  What is your thinking behind wanting to keep it at 50 apart from lowering water usage?

For difficult to read results you can take a photo and use something like this to try to manipulate the photo to grayscale or another color scale and try to make it easier to read. I use this one and it has 2-3 that usually work well given the original colors.

https://www.color-blindness.com/coblis-color-blindness-simulator/

Edited July 10, 2022 by nabokovfan87

[ScottieB]

How about diluting a sample? Say 50% tank water and 50% zero nitrate water (prob not tap depending on where you live). Then see if you get something closer to 25. If it’s still shows really high your nitrates are more then you think. 

[Melkor]

How old is your api nitrate kit? Mine was fine for 6 months after purchase. But then no matter what it was showing 20+. Tap water, tank water before and after water change. So I got ACO test strips to compare and it was in line to what I'm used to seeing. From a bit of reading I saw api had issues with their ammonia and nitrate liquid test kits reliability over time. My ph and nitrite from my master test kit seem fine, and so is the kh and gh tests I bought separately.  Maybe try a new liquid kit, or another brand. I am hearing good things about sera and salifert freshwater nitrate kits.

Edited July 11, 2022 by Melkor

[Philip]

I would take a sample to someone else, like your local fish store and see what they get. If I had to guess I'd say your test strips have reached their expiration date. 

One thing I will say, as a chemist, the Aquarium Co-op test strips that I have used have been dead on, and I spot check them against expensive equipment that I use in a lab. 

Good luck,

 

 

[Guppysnail]

@GreenCircleGirl I have the same issue. I have been keeping fish almost my whole life. 
Testing for nitrate used to not even be a thing. I was reluctant to switch to coop strips. Api though I tested weekly seemed awful because it was always red like yours and I struggle to differentiate colors. I have been using the coop strips since they came out. I worried the same as you because after years of rarely seeing less than 40 with api I was now seeing 25. I did use several other test kits and had hubby help me check colors against coop strips. I also used a digital one and the coop strips were spot on. Since I have become comfortable with coop strips I have had zero issues in my tanks. My fish all still breed my plants do fine. 
Cory even mentioned water treatment facilities buy these in bulk. So that is very reassuring. I hope that helps ease your mind. 

[GreenCircleGirl]

Thanks for all of the answers. I’ve decided to use the Aquarium Coop strips and go by those readings and to just stop stressing about the incongruities. 

[LaloJ]

I had no idea salifert handled kits for fresh water, if so then I would swap API for salifert. Do the test with half the water from your tank and the other half fresh water as suggested above and see the result, if you get high nitrate it means that the API test is correct.