Welcome to AA. Most people here would say that using tap water is a no-no. Long term using RO
water is the best because tap water has impurities that build up over time and could cause a crash after a certain period of time (this timeframe is not exact given different water parameters in different areaS). I myself filled my 29 gal
tank with tap and have done every water change since with bought RO
water until I get the energy up to by an RO
filter. My tank will be one year old in the next couple of months and my clowns have done really well. FYI - nothing is cheap in saltwater...good luck and keep reading...