I have a 20 gallon aquarium which my brother gave to me, but he didn’t give me any supplies for it. I had to go online to see what all I would need. One thing is if you are doing fresh water or salt water there are some different things you will be needing. I have no idea how the salt water works at all, but I do know fresh water somewhat. First I got a book about how to set up a fish tank, I know some of the things I will need and that is a filter, some kind of stone for the bottom and also a light for the top which is usually built to sit in the hole of the tanks cover.