I'm not going to tell you what to do, but I wouldn't use tap water. When I re-did my tank and used about 20 gallons of new spring water, all the nutrients in the water sparked a huge algae bloom. It's starting to die off now 4 months later. It's been a pain. I had diatoms for a good 3 months and now on the 4th month, thank goodness its cutting down and I only have some detritus and green hair algae. I advise to use ro water. If you dont have an RO unit try getting some distilled or RO water from the fish store.
We all learn the hard way, including me, so all I will say is BE CAREFUL.