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Aquarium Co-op test strips vs API test kit question


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Hi everyone, I've been using my Aquarium co-op test strip for about two weeks now and I'm loving them, but I've noticed the readings I get with them are different than the ones I get with my API test kit (not the strips, the tubes). I'm more inclined to trust the test strips than the API kit because I know how much testing goes into Aquarium Co-op products, but I was wondering if anyone had similar experiences, and what ended up happening.

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I used both at the same time, and from what I saw, both of my kits showed the same ballpark water parameters. I'm tempted to find out which is more accurate, but that would require me taking water samples to a county water treatment facility and for a price.

Overall, I'm sticking with the Co-ops strips due to value and that the colour chart is better. The API chart is a double sided peel out, and once the adhesive stops working, the label flaps around. Yes, it's such a minor detail, but it's enough to make me switch to the Co-op strips.

Just go with whichever brand you feel is best! Both seem reasonably accurate.

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Against popular belief, I find the API liquid test kits to be inaccurate due to human error a lot. Not saying you did anything wrong, but drop sizes can vary, tube fill amounts can vary, the Nitrate test needs to be banged and shaken like crazy to be accurate from bottle two and the Ammonia test is NH3 and NH4 which really reads ammonia and ammonium, not just ammonia so it does not give an accurate ammonia reading, you need to calculate it yourself based off temp, PH and NH3+NH4. 

In other words, I prefer test strips, just dip and read, takes user error out. 

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47 minutes ago, awymorePDX said:

I don't have the ammonia test strips, but it makes sense that they would be close as ammonia is pretty much a constant value in a correctly cycled tank.

I see my biggest differences in the PH, I need to do another AB test, but they have been more than 1 point different

Oh yeah I forgot to mention, the pH readings using the API test kit are always significantly more basic than with the strips. It would make sense that the strips are more accurate though, I’ve been losing my mind trying to figure out what is bringing up the pH in my tank, but the strips put it at just barely below neutral. That reading makes more sense given that tap water is neutral or ever so slightly basic, and the nitrogen cycle brings the pH down

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I suspect lots of this comes down to testing methods, possible contamination, not waiting correct times etc. The strips were tested vs known scientific solutions. They were right on. Then we tested with sterilized API kits, and digital meters. All were very close in our testing, which was done by myself, Randy, and Dean. We also had the store using them for a few months before going into production. I don't want to stifle people's tests. By all means keep testing etc. I think the test strips are accurate, especially for the level that an aquarist would need.

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Coincidence! I just looked at the object I am working on, a digitized page out of a notebook from a 1920s era nursing student:

"Litmus paper …
If it turns paper blue alkali
If it turns paper pink acid."

Oh, if only the colors were that obvious! As Hobbit says, I struggle a lot with determining the right color, especially for the API nitrate test. I bought a container of Tetra test strips on Amazon, but I look forward to running out so I can justify buying Aquarium Co-Op's test strips.

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27 minutes ago, Celly Rasbora said:

As Hobbit says, I struggle a lot with determining the right color, especially for the API nitrate test.

I like and trust the API liquid test kits to a degree, but I have this same difficulty with the colors of the Nitrate and with the high Ph colors.

For me, personally, if a test gets me in the ballpark, I'm happy with it.

What I look for in a test is that it's consistent between readings in a water sample that hasn't changed. This way when I take two readings I can be like OMG that was light orange yesterday and now it's deep red, something is up!

I use test strips more often than liquid kits, and with these, I'm just looking at trends -- how much has the color changed for any given thing since last reading, and in which direction is it headed -- up or down.

I stopped trying to differentiate between the shades of color for something like 10ppm vs 20ppm nitrate, or 6.6ph vs 6.8ph. However, if Ph was lightish green and now it's a deeper blue, that's meaningful enough for me.

I am eager to try the Coop strips, as the price is good deal for the quantity of strips.

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13 hours ago, GardenStateGoldfish said:

Against popular belief, I find the API liquid test kits to be inaccurate due to human error a lot. Not saying you did anything wrong, but drop sizes can vary, tube fill amounts can vary, the Nitrate test needs to be banged and shaken like crazy to be accurate from bottle two and the Ammonia test is NH3 and NH4 which really reads ammonia and ammonium, not just ammonia so it does not give an accurate ammonia reading, you need to calculate it yourself based off temp, PH and NH3+NH4. 

In other words, I prefer test strips, just dip and read, takes user error out. 

I'd never thought of this but you're absolutely right, there's a lot more room for human error with the liquids test kit, especially if the test solutions get contaminated, or if the water partially evaporates off and changes the concentration

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I have to agree with @tolstoy21 on this one. My aging eyeballs has difficulty telling 40ppm and 80 ppm nitrate. (Which has often made me wonder how a person who is legitimately color blind navigates this issue.) Ball park readings is what i am mostly going for. Any drastic changes are my alarm bells that tells me something is wrong. I also will admit that i dont have very fussy fish. I could see where more delicate fish with larger margins of error could come into play, but again if your new test strips are accurately reporting consistency or lack there of, i feel like it is doing what it was intended to do. 

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