I have had Alex, my goldfish for 15 years now and she is about 5 inches. She has moved tanks, her last one being a 60 lite Biorb which I ended up getting a Stingray filter for as the Biorb one was ineffective.
I have been worried that she has has not enough size in her tank for a while and eventually decided that a pond would suit her better. Especially as she is paler (our house is very dark) and my research told me sunlight my help.
I live in a rented house so cannot dig a pond. As a test, I have put her in a 125l plasterer's bath which she seems to like the length of, but the depth is less than a foot and she is sitting on the bottom alot which, looking on these forums, looks like a sign of stress.
I have researched every 200 litre and below pond I can find (I have a lower end budget so can't really splash out) and have found a couple that look like volume-wise they will sustain a solitary fish. However, none of them are over a foot deep and I believe she would need 2 feet to be protected against the heat and cold. Examples are the Loglap style ones and the Blagdon Affinity Half Moon.
I was wondering if someone can recommend another brand that will suffice?