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Discussion Starter · #1 ·
I have a seachem phosphate test that I bought about 18 months ago. I'm not convinced that it's at all accurate now.



Top is my tank water (I dose Thrive about three times a week).

Middle is RO.

Bottom is the 1.0ppm reference solution that comes with the kit.

I recently had to replace an API hardness test kit, because I discovered the GH test never changed color.

Should I be using better quality tests? Lowering expectations? Replacing them more often?
 

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My API Ammonia test expires 1/2026. My API Nitrite test expires 11/2025. I am forcing myself to use some API tests because that is what millions of other hobbiests are using and I feel like I'm cheating not using them. The technical support representative at LaMotte told me tests last two years. That's my new guideline. Shelf dates will vary by the type of tests and storage conditions. I once ruined a vial of Nitrate developing powder by somehow letting it get damp. That had a bad consequence because I went on trusting the test results. There is information here on TPT about how to calibrate your tests. When in doubt calibrate. Your comparison of the three samples was good. You can also test samples of known concentrations that you mix yourself.
 

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Discussion Starter · #3 ·
I once ruined a vial of Nitrate developing powder by somehow letting it get damp. That had a bad consequence because I went on trusting the test results.
Yep I was using a bad GH test for a long while, not realizing it was bad. I just thought my water was really hard and couldn't figure out why. The KH test was never too high, so I was stumped. In the end, I concluded that

a) the GH test was no good; and

b) I actually was concentrating minerals and dissolved solids by topping off evaporation loss with more tap water instead of RO.

I don't test things like phosphate and iron too often, but I'd like to know that the test will work when I need it. This phosphate test doesn't have an expiration date, or even a lot number on it.
 

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b) I actually was concentrating minerals and dissolved solids by topping off evaporation loss with more tap water instead of RO.
For sure, mind your GH. I did the same thing for a couple of years. The water got hard and I was like, huh, what's going on? Then my inner chemist told me it was me concentrating my solids. It was either my inner chemist or someone on the forum. I can't remember. I have two different tests for GH. they're both high quality tests. One is a powder you use with a colorimeter and the other is a good titration test sensitive to within 4 ppm CaCO3. I have a really dilapidated aquarium but very good tests. It's actually not even my aquarium. I run it for someone else.
 
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