Zero nitrates and 0.25 ammonia suggests no cycle is happening... when did you last check ammonia or have a positive nitrate reading? My nitrates always measure as something, however low, so I don't bother with ammonia... if nitrate came in at undetectable then ammonia would be tested immediately.
Did you manage to recover the two dead fish which were missing? If not then this would account for the ammonia reading I guess. If you have then what's happened to interrupt the cycle?
Did you manage to recover the two dead fish which were missing? If not then this would account for the ammonia reading I guess. If you have then what's happened to interrupt the cycle?