What's wrong with paper test strips?

[ZonaGirl]

I just read on here that I shouldn't use paper test strips. Why is that?

I have a test tube kit for ammonia and nitrite, but I bought a paper kit for the nitrate. I'm wondering if I need to take the kit back and buy the test tube style nitrate kit.

 

[Pure]

Because they often do not give you accurate tests. They are normally off .5 to 1.0 in their readings.

 

[Submariner]

Another problem is they don't last, once the bottle has been opened and moist air gets in, it can contaminate them.

 

[noncentric]

Yep, it's mostly a matter of air (as Submariner said).

Once the bottle is opened, then the reagent chemicals in the test strips start to 'decompose'. As time goes by, the test strips become more and more inaccurate.