I have just read that link myself and realise I got the tank size wrong So I have amended post #12 with the correct volumes. My apologies for the incorrect information.
Fancy goldfish need 100 litres/26 gallons for the first fish and 50 litres/13 gallons for each additional fish. So 3 fancy goldfish need 200 litres/53 gallons.
Fancy goldfish need 100 litres/26 gallons for the first fish and 50 litres/13 gallons for each additional fish. So 3 fancy goldfish need 200 litres/53 gallons.