When I wrote that the bacteria ate the Amonia I should have added that the Nitrite and Amonia levels returned to zero after 12/18hrs.
That would suggest that the tank is cycled, don't you think?
During the whole process the Nitrates have steadily grown so a 100% water change was necessary and now we are maintaining the filter with a few drops of Amonia every day.
Hope this makes it a bit clearer.