Totally! I had to over winter the poor fish in a 20g...
I am going to get them a bigger tank for next winter though.
I'd get them a big Rubbermaid tote or go to a farm store and get a watering trough of some sort.
be moving this summer to my mom's house where I grew up, she's moving to a new house and giving me her house, so I want to build a pond. Nothing big, 500g or so. I'd like it deep enough to be able to leave the fish in though. I need to do lots of research first because I have no idea about ponds other than they are awesome when done right.