What is going on with my water?

[Donno]

I did a test of my water a few days ago with a API test kit and tested for ammonia, nitrites and nitrates. I registered .5 ppm ammonia, .5 ppm nitrite and 0 nitrate. I cycled the tank months ago and my current fish have been in the tank for 6 weeks and appear to be healthy. I spent the money to buy the Seachem ammonia test kit since I use Prime and it shows 0 free ammonia and 0.2 total ammonia.

I do a 75-80% water change every day using tap water treated with Prime.

I can't believe that I've lost the cycle without doing anything to the tank other than water changes.

Any ideas as to what is going on?

[mcishaque]

API test kit reads false positive on ammonia when Prime is in use. That has been my experience.