You will need at least one power head for flow, probably 2. What's your plan for the tank? If trying reef I highly recommend using ro
water, tap water will cause you all sorts of headaches in the future. I would also recommend a refractometer for measuring salinity, much more accurate than hydrometers. There are some great articles in here about cycling a salt water tank, most people use a raw shrimp from the grocery store or pure ammonia to start the cycle. Will take about 3-4 weeks. Just know too that you will need to clean that canister weekly as they can build nitrates, they are not commonly used in salt but some people do and have had success. A protein skimmer would be a better investment...