I think bigger ponds/tanks are easier to regulate parms. due to water volume. However, I have done water gardens in a half-whiskey barrel planter and they were really nice. It is just a matter of getting a good balance (working with mother nature, not fighting her). Small ponds just need a little more attention upfront, and they to become almost self-sufficient w/time. Basically I'm saying if anybody out there is thinking about a pond DO IT. They can be as big or small as the area your working with. I will also say that I always hear people wish they had gone bigger. A little more time spent planning and research will pay off in the end. I currently in the process of planning my next pond. I will make my current pond the filter for my next pond, flowing into a stream about 8' long, then dump into 4K+ pond. This however hinges on the sale of our house. Since the market sucks, I may be staying at my current house and upgrading.