I’ve see people run as little as two power heads and live rock in fish only tanks. There are a lot of ways to set up and run a system. Hardly anyone uses tap water. If you are going to try that then you better know what’s in your tap water and be prepared to deal with a possible algae out break because of it. Then you will have to deal with that and stop using tap water. Can it be done sure is it worth the risk to me no.
Also, hit up local reef friendly stores in the NYC area - even if you buy one live rock and use dry for the rest, it’s a great way to seed growth of all the good stuff [emoji3481]