Is it possible that you are not getting the nitrate test processsed correctly? I have problems with mine - for the chemicals are not used in equal amounts. The second bottle of the AP test has a larger drop than the first bottle - and runs out sooner. I swear that the mix at the end is not quite right.
If you are using the AP test, remember to REALLY shake the 2nd bottle for 30 seconds - count it or time it, do not guess! - and then after the addition to the test tube, cap it and shake it again, vigorously, for 1 minute - timed.
I do not know why you are not seeing nitrAtes, but .25 ammonia is really a small amount - with the fish you have in that 20, assuming you are feeding them

, if you did not have a cycle, your ammonia readings would quickly rise over 1-3ppm, not stay at .25ppm.
It is entirely possible that your cycle has developed slowly and gently - the nitrItes being processed at the same time as the ammonia - both types of bacteria deveoping concurrently. This is the best of all worlds in a tank cycling with fish.
Since you are always going to need to nitrAte test, if you have any doubts about it, you might consider getting another one to see if there is something wrong with the first. Then change change change that water - do not be afraid to change it out.
I have 3 tanks (30s and 20) that are obnoxiously sticking to about .25 or a bit under ammonia for weeks after their "cycle". To conquer this, I have added extra media for the beneficial bacteria to colonate in hopes that the larger colony of beneficial bacteria will grow to process that last little bit.....
Patience - it will get there..... honest!