Just so you know, an aquarium heater does not use THAT much power. It's not on all the time, just when the temp needs to be raised in the tank.
Your fish will not live at those temps very long. You may want to look into coldwater fish if a heater is not an option. they are TROPICAL fish (tropics..warm areas..bahamas...ya know?)
which means they need temperatures that are in the high 70s-low 80s.
Heater + rock salt (kind you use for ice cream, make sure its food grade) will cure ich in livebearers and will do less damage than most meds. Livebearers are incredibly tolerant of salt, mollies can actually be slowly adjusted to live in seawater.
Malachite green medications will work, but it can be hard on the fish, and it will stain everything in the tank green.
Sorry people were so argumentative over things. shoot me a PM if you need any more help.