So I have this huge rain barrel connected to my barn/shed. the roof is huge, so a good amount of water would get in there every time it rains. I was wondering if a could through a few fish in there. I know this is a dumb question would this kind of thing need a filter, or would the rainwater be enough? It gets pretty cold in the winter here, there's a 3-inch sheet of ice on it at most but it has never frozen solid. What kind of fish do you think it would be good for? I like the idea of shubunkin goldies but IDK.