If you don't want to use ammonia - why not use fish food or a piece of prawn?
because A it works out expensive for the fish food, and you cant control the amount of ammonia put into the water. where as i can with the fish in. although i could use a prawn to control ammonia i dont see the point, because really you could end up doing daily water changes so there isnt too much ammonia etc.
the only plus side would be that you wouldnt harm fish, but ive only had to do fish in twice, i now do clones with old media