If I am reading your post correctly, you are experiencing high ammonia in a fish tank without fish? Even after multiple large % water changes?
It can only mean one thing, something is rotting in your aquarium. Either a dead fish, or some leftover fish food or too much fish poo. Or something else organic. You must use an aquarium vacuum to suck up as much debris as possible from the bottom of the fish tank when you do a water change.
The "bacteria boom" was not the cause, but rather an after effect when the cycle had been crushed or at least it entered a mini-cycle because too much ammonia was produced, and the good bacteria colony in the filter media was not enough to handle it. So bacteria multiplies to meet the "demand" of ammonia production. What you need to fix isn't the bacteria boom itself, but rather to get the tank fully cycled again, or get rid of whatever is producing the enormous amount of ammonia in there (without the fish?)
