Its been years since I had fish. Was a founding member of the Taieri Fish Club many, many years ago. Like 35 / 40 years !! I'm more into cold water varities, Leopard fish, Mountian Minnow's etc but do have Platies and a Koi Swordtail all in the same tank. The tank is not heated as my office is a solid 20 - 24 degrees all the time.