How often should Ranchu goldfish water be changed?

Change Ranchu goldfish water about every 3 days. Best kept in a bare tank with filter, air pump, and heater, holding temperature at 20 to 25 C, since too high or low harms growth.

When weather changes sharply, use the heater to steady the temperature and avoid sudden swings. Also change water regularly and clear food residue and waste to keep water clean.