Help With Api Test Result Please

[anon02]

Up to recently I`ve been using Tetra liquid tests, since they ran out I`ve been using API liquid tests

I had been having a problem telling the difference on the purples of the nitrite test so I decided that any colour other than blue meant I had an unacceptable level of nitrites

Here`s the problem, when I test my tap water which I know to be 0ppm nitrite, the drops in the test tube are blue and stay blue, but when I test my tank water the drops in the test tube turn purple but after 5 minutes, they have turned to blue, are both the readings a true zero ?

 

[Harlequins]

If the nitrite is blue to start with and doesn't change its zero...

If the nitrite is purple to start with it usually means the nitrite is off the scale

 

[Katch]

yeah - if you look at the test and its any shade of purple then you have too much nitrite. If the drops turn purple in the bottom of the tube before you shake it - then you are off the scale.

A proper test will develop after 5 minutes and then stay that colour indefinitely (when I'm being too lazy to rinse my test tubes I end up with a row of different colours from different day lined up and they don't change after the first 5 minutes)

If your test is going purple then blue - I'd suggest you are doing something wrong.

Make sure the test tube is well rinsed - no left over residue from previous tests.
Add 5ml of tank water and 5 drops of reagent.
Cap tube and shake hard a couple of times (you have to press down on the stopper quite hard with the API tubes to stop liquid escaping round the edge of the stopper)
Wait for 5 minute then read.