Apart from Chlorine and Chloramine, tap water in certain areas can have unexpected occurrences of Heavy Metals, such as copper from old piping, which is lethal to livestock.
It is extremely rare for tap water to contain Ammonia. Rather, it is often released within the tank: when we stir up decaying matter buried in the substrate, when there is livestock death or when the tank’s biological filtration system fails and there is a surge in waste matter.
Sudden spikes in Ammonia and Nitrite (an oxidised form of Ammonia) can melt plants and kill livestock.
*If you are keeping more sensitive fish or livestock, it is best to pre-mix it with tap water, before adding the water into the tank.