You might not actually have a cycle because if there has been no source of ammonia for a month the good bacteria might have died off. If I were you I would try adding SMALL amounts of ammonia and see what happens to your conditions over the next few days, if the ammonia rises but nothing else does then you will have to start your cycle over again. As for the diatom bloom I agree with melosu58, in that it can very. What will affect it is the grow of the good stuff in your tank, such as green algae and coraline.
Are you running carbon? What about phosphate remover? Anyways good luck and keep us posted!