I was hoping to find a cost effective way of heating a pond of around 2000 gallons maybe more. I heard that you could take a large plastic storage box and cut and entrance hole for the fish and just keep this box heated. How effective do you think that would be? Are there any other ways of keeping the pond livable for cichlids or other tropical fish other than out right heating it? I live in SoCal where the winters are pretty mild. The average temps in the winter are probably around 85-60 in the day and 65-40 at night. I was hoping to keep cichlids in the pond. What kind of fish other then koi and natives could survive the winter without any heating at all?