Is there any goldfish suitable for a 5-gallon tank?

Platies aren't bad for small tanks, but just make sure you buy all males or you will have fry.
 
MCMM love them so much
 
White Clouds are suitably sized, will do very well in an unheated tank, and will likely breed. There was a year when someone brought me some that had survived a winter in an outdoor pond in Philadelphia. It was a warm winter, but still, those fish survived high 40s water temps.
 
After going over all this with my daughter, and looking at some LFSs today, she's decided on a Betta and likely a couple Mystery Snails. We can get a 50W heater cheap enough and then we'll never have to worry about tank temps. In our journey today we saw a couple larger Fancy Goldfish, which was helpful so she could see how inappropriate they would be in a small tank.

Now I just need to get the 5g tank set up and cycled (should be quick since I have media from my 29g tank to kickstart things), and then we can make one Betta's life a lot better by giving it a proper habitat. Thanks for all the input, everyone!
 
Both good choices. Personally, I'd suggest a female betta over a male. I think the females have more interesting personalities.
 
i can't put anything with my female crowntail betta. for her tiny size of an inch and a half, comparatively one of the meanest fish i've ever seen. she's so filled with anger.kills everything in the tank. but she's one of my very favorites. because she's so darn grumpy.
 
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