Ammonia 0.25ppm 5min After Test , Open 1hr After ?!

For the past 3 days or so , ammonia of one of my cycling tanks (90gal) has always been 0.25ppm ( a very slight green ) 5min after water fest ( as instructed by API master test ) , but it always dropped to 0ppm ( totally yellow ) 1 or 2 hours after ?!?

Which number should I believe ? Can I assume the tank has 0 ammonia ??

I only have 2 baby fantail in this tank

 

Well, it seems like your bacteria can process .25ppm in just 2 hours!

 

But how come my nitrites level Is 2ppm 7 hrs after 90% water change (I think it's 2ppm ? The colour chart provided by the API test kit is very confusing

 

The 5 minute number is the correct number.

 

The 5 minute number is the correct number.

 

Maybe that wasn't the answer you were hoping for.

 

Maybe that wasn't the answer you were hoping for.