The first thing to say is that ammonia can be hard to read. A lot of people report that they have never seen the zero colour even on tanks that have been running for years. Have you tested your tap water to see what the ammonia reading on that is? If that's also 0.25 it could be that you are one of those who always see pale green even when it's zero. Light can also affect the test if you are reading it under fluorescent tubes or energy saving bulbs.
Nessler based ammonia testers (and most of our liquid regent testers are Nessler based) are affected by Prime. From Seachem's Prime FAQs
A Nessler based kit will not read ammonia properly if you are using Prime®... it will look "off scale", sort of a muddy brown
Since your nitrite is zero, can I suggest you use
this ammonia calculator. It tells you how much of your ammonia reading is in the more toxic ammonia form. Since the proportions of ammonia and ammonium are pH and temperature dependant, using a calculator like this is a handy tool for each individual tank.
On the left side, leave the first box as it is. Enter your ammonia, pH and temp (which can be changed to deg C) and set salinity to zero. Then click calculate. The number you want is the lower one on the right hand side, the one labelled NH3 concentration.
If that number is below 0.02 it is safe to leave longer between water changes. You only need to do the next one if your ammonia reading increases until the calculator reaches 0.02.
I suspect that after six weeks you'll find your ammonia reading does not go up even without doing daily water changes. If this is indeed what happens, despite a reading of 0.25 the tank is cycled, and you can start adding more fish, a few at a time.