I like the idea of putting them under a rain spout on your house. Im thinking burying a plastic barrel in the ground 3/4 of the way to the top, divert your rain gutter into the barrel, drill a hole 5 inches from the top, and glue a piece of window screen over it for a drain. Cover barrel with some hardware mesh to keep animals out and let fresh water flow in when it rains. Feed them flake food once or twice a week, if you want to keep large quantities add an airstone/bubbler. When it doesnt rain, just dump in a 5 gallon bucket of tap water once a week or whatever, Id guess that even without declorination, 5 gallons in a 30-40 gallon barrel of water wouldnt kill the fish. If you dont bury it, it would likely get too warm during the summer and youd have significant dieoff.