Once the tank is fully cycled and fully clear of ammonia so that you know the good bacteria are doing their job, stop testing for ammonia. False tests will only drive you to do dangerous things. If fish act weird, then doing some ammonia testing is good but not to worry with tiny amounts. False test results are often reported. Keep in mind that tests are only that, a test, nothing more. You have a test that says there is a problem but fish that say there is not. Go with the fish. Testing should be looked at as an indication, not a solid answer in many cases.