I lost my goldfish from his hospital bowl last week (RIP Ratis) So now I have this fish bowl. How much water do I need? Its not a big bowl so if its too small I could stock it with Guppies? How do I heat the water or is it okat not to atm as it is summer and usually about 90F during the day? But wat about for winter? What about a filter? Its only a smallish bowl so would I even need one?