Join Date: Oct 2010
Location: Victoria, Australia
I agree. Not only will the goldfish have more space, but goldfish are high waste/ammonia producers and in a small container (most of our Tupperware is a gallon or less), this is going to build up very quickly.
Neither the tank nor container are cycled, so you are still going to have to be doing very frequent (and most likely very large) water changes. However, the 10 gallon sounds like it offers more water volume, and this means that it will take longer for the ammonia levels to build up to toxic levels than it would in the Tupperware container.
I also wanted to say that with a goldfish, you want a filter with not only a good turnover rate (a lot of keepers suggest that your filter be capable of turning over ten times the volume of the tank an hour), but also plenty of space for filter media. Those smaller filters aimed at nano tanks (and usually designed for low to moderate stocking level) are not suitable. Goldfish get big, produce a lot of waste and are very oxygen hungry fish.
Also, as someone who has made multiple mistakes with their goldfish care, I would personally consider upgrading to a suitably sized tank now. I understand if this is not possible, but I stunted my three shubunkin by having them in an improperly sized tank. I think with goldfish, it is better to have them in a tank that is appropriate for their potential full size from the beginning. Often you waste more money upgrading tanks than if you'd just gone out and purchased the bigger tank at the start.