Tap water contains chlorine and chloramines, which are added to our water supply to act as a disinfectant. They are very
effective at keeping the water clean for human consumption, but unfortunately fish cannot tolerate chlorine or chloramines.
You therefore need to add a de-chlorinator (try using King British De-Chlorinator
to the water before adding it to your aquarium. In all other aspects, tap water should be perfectly safe for fish. However,
it is also good to know the hardness of your tap water.