The shape of a fish’s mouth may largely determine its mode of life. For example, you’ll find a turned-down mouth (inferior position) on bottom-dwelling species such as Catfish. These fish feed in mud, sand, or gravel, and off flat rock surfaces and plant leaves. A mouth located in the terminal position points directly forward from the fish’s face. Common among species such as Guppies and Platys that swim in midwater levels, a terminal mouth facilitates “picking off ” food as it sinks toward the bottom or floats in the water column.
The Betta’s upturned mouth, known as the superior mouth position, enables it to feed efficiently at the surface. Bettas snatch small insects and mosquito larvae from among the floating vegetation in the pond or paddy. They also greedily scoop up flakes at the top of the aquarium.
Always take care to ensure that your Betta receives its fair share of nourishment, especially if it is living in a tank with faster swimming, more aggressive fishes. Add food that sinks together with food that remains on the surface. Don’t force your Betta to compete with mid- and bottom-dwelling tankmates at feeding time.