Be careful on the validity (a test that measures what it is supposed to measure and nothing else) and reliability (how acurately it measures what it is reading) of test strips. You may have no ammonia at all in your tank. To be safe, I would do daily partial water changes until I get a liquid test kit.
No smell, no strange behavior, seems to me a strong evidence in the direction that your tank is not holding 6PPM of ammonia.
Keep in mind that even with liquid reagent tests you could get false positives.
For instance API Freshwater test for ammonia, and most out there, use Nessler reagents, which under certain circumstances, e.g. after medicating with formaline (present in some Ick formulations), or adding water with chloramines (e.g. a faulty dechlorinator product), give false positive readings. These liquid test kits, however, are valid and reliable enough to be quite useful for our purposes.
Fish are quite intolerant to ammonia and nitrite poisoning. Their behaviour should tell you something about this.
Pepe
Santo Domingo