I'd try for 60 or 70% water changes if the ammonia is reaching 0.25ppm by the time you are able to change again, it just means gravel cleaning a few minutes longer as the water line falls a bit lower past the halfway point.
Today result was Ammonia 0ppm and Nitrite 0ppm i did a 50% water change and ill test same time tomorrow and if still 0 and 0 i will do know water change.