None of these fish need an aquarium heater. Feed them twice a day with fishfood flakes, pellets and wafers. Make sure that they get along with each other.
All three of these types of fish have the same needs. The most important thing in a tank is the air. Make sure you have a sufficient pump and bubbler in the tank. You can pick up Koi or Goldfish food at any pet store. You do not need to heat the tank.
