One of the largest freshwater fish is the Arapaima. It can weigh up to 400 pounds and inhabits the Amazon region. The probably best place for fly fishing for large Arapaima is Pirarucú in Brazil.
How do you fish for Arapaima? The flies should be large streamers with a lot of water displacement, around 20-25 cm in length. Personally, I found that the color of the streamers didn't matter much. While Jako and the others caught most fish using black ones, I caught mine with light-colored flies. Most bites came in deep water, so we fished with sinking lines. The fact that we were constantly surrounded by Arapaima heightened our excitement.