Waiting The 5 Minutes For Ammonia, Nitrite, And Nitrate Tests

[marleth]

When testing the water, sometimes I wait longer than 5 minutes to take the reading. Does this affect the validity of my reading? I am using the API Freshwater Master Test Kit.

Same question goes for the pH tests. If I don't take the reading immediately, can the colors change if I wait too long?

 

[Corleone]

In my experience, the pH test is fine for quite a while, but the others will change color over time. After about 15-20 minutes, my ammonia tests turn a dull brownish yellow, regardless of what shade of yellow or green they were. The 5 minute mark is where the tests are calibrated - past about 10 minutes I wouldn't trust the results.

I also found leaving the tests in overnight (which has happened several times by accident) causes a brown residue in the tubes over time. If you get that, it's easy to remove, though - fill the tube up to the line and add about 10 drops of nitrate bottle 1 (which contains a strong acid), and shake it, should come out sparkling.

 

[Mr Bliss]

The Tetra nitrate test tells you to wait for 10 minutes, although I've never seen the color change after ~5 mins or so. Since the chemicals used are most likely the same, I guess 5 - 10 mins is a safe margin, after which the test starts losing it validity.

 

[doresy]

My guess is the instructions are there for a purpose so why want to ignor them?

If you want it to do what it says on the tin, do what it says on the tin!

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[puppyjess123]

yep i agree with dorsey. They wouldn't put on the instructions if they were wrong would they?

 

[waterdrop]

I agree with dorsey. The tests are not valid at wait times other than specified. My father-in-law is a dye chemist and said that in order to design the type of continuous-change color match test you have to worry about a range of other water conditions that might be included in the sample other than the thing specifically being measured. Any one of us members might watch our sample beyond the correct 5-min mark and decide it didn't change much but that doesn't mean it would be true in the wide range of possible cases.

I happened to have one of those little kitchen timers that comes on a cord to go around your neck. This is perfect for letting you do other things for the 5 minutes and still go back for the reading when the beeper goes off. Its also great for timing the shaking stages for the nitrate (NO3) test, which are essential to have any hope of a correct reading.

~~waterdrop~~