Not exactly a pond, but they will be outdoor. They're 55g plastic "drums" that are 23 inches in diameter and 35 inches tall. I've heard of people using them for fish and I've seen them posted on freecycle/craigslist so I'd like to get some one day to use for fish. Not sure what kind though, what kind would be best for the size of it? Basically any tetras, guppies, and other small fish?