I guess there's no heater either, as these really are tropical fish and should be kept as such. Just remember that without filtration, if something goes wrong, it will go wrong very quickly.Yes, but goldfish prduce truckloads of ammonia more than a betta. There's no comparison.I have a tiny but effective filter in my 18l (4gal ish)coldwater tank for my one goldfish who is thriving better now than he ever was with no filtration.
The water is better for him as there are no growth inhibitors kept in the water and he is now almost to the size where i should get a bigger tank! And i've had him for about 5 years now!!!