I recommend the 'silent cycle' for dealing with residual ammonia. Plants take up ammonia, faster growing stem plants take up more. If you plant like 50% of the substrate with these they will take care of the ammonia and the Nitrogen cycle will develop at its own rate.
I do see there might be a problem with the stem plants if you want to remove some later because the roots may pull up soil. Stem plants really don't have much in the way of root systems though.
This thread has been educational. I'm trying to get used to the idea of MGOPM and how to do it.