Thank you for the fair warning ;). I hate to throw numbers out but I have a 29 gallon waiting and I want to get just one goldfish. Some people say they need other goldfish, some say they are fine alone. So a single goldfish is fine?
SURE the catch is that by the time you get an aquarium large enough for one Goldfish you can keep multiples. The biggest mistake made with Goldfish is they try to keep them in aquarium that aren't appropriate in size. I will also caution that fancy Goldfish are not an easy fish.