There are adapters that allow you to hook up to various faucets and hoses. Myself personally I wouldn't and have never bought seawater from the store. A 250 gallon bucket of salt is about $50 or so and that comes out pretty cheap per gallon. At a later time, you may also consider setting up an ATO for your tank and the RODI would be invaluable for that. Lots of different things to think about, but you came to the right place and you are asking the right questions. Good luck!