orandas can reach a foot in length and black moors can reach around 8 inches, so ideally you really should go for a minimum of 3 feet, if you can find a cheap stand (make sure it can bare the weight) a 3 foot tank from a pet shop will cost next to nothing, when i brought mine for my gerbils it was around £40. obviously you will still need the hood,lighting,filter etc but it may be a cheaper way of doing it. whatever tank you get, you will need to make sure you gravel vac and partial water change at least every 2 weeks, especially for goldfish like these as they are poop machines. i agree to advertise on freecycle or such like sites, they are always being given away. good luck