For those who don't understand the process, or have new set ups where the tanks bio is not fully mature, and/or the pH is high, and/or they keep their fish in warmer water, and/or they don't have tanks full of plants, or your local water supply uses higher levels of chloramine during certain times of the year, there is a caveat to what Duane posted.
Exposing fish to NH3, free ammonia, is like exposing an infant to second hand smoke. There is no "good" amount or value, to a fish.
NH3 (free ammonia) is toxic, to all fish, even small amounts of NH3, and even for short durations. The higher the pH of the tap water, as well as the higher the water temp, the more toxic it becomes. A good article on that subject can be found on the Krib.
https://www.thekrib.com/Chemistry/ammonia-toxicity.html
HTH