They like hard water, so dechlorinated tap is better than RO. As adults they should have a minimum of 10 gallons per fish. No heater necessary. They need well aerated water, especially when it's warm. Feed once/day with a day off each week. They need veg in their diet. Some will eat lettuce if they were raised to take it, most will eat duckweed, anacharis, cooked and shelled peas are great. Give them the veg at least once/week with a good goldfish pellet food. 10 yrs is a typical fancy goldfish lifespan.