DONT BOIL WATER before putting it in the tank.. UTTER waste of time & in fact I heard reports that actually using boiled water is not a good idea...
Boiled water has little oxygen in it.
Boiled water has no buffering capacity as the calcium which forms the buffers has been 'boiled' out. Over time it could lead to low KH levels in the tank and eventual pH crash.
Also remember something about fish getting the bends (yep, same kind of thing divers get)... but that's probably utter nonsense?
^ I am repeating that lot parrot-fashion with no understanding of wether those claims are accurate.... make your own research.
Andy