It’s important to know which species of tetra you are talking about when you are deciding on species that will coexist well with your tetras. The smaller tetras, such as neon, lemon, ruby, serpae, black phantom, cardinal and glowlight tetras, typically grow no larger than 2 inches and are a favorite in many community tanks. You would not want to put tetras with oscars and gouramis, which can grow quite large and will likely consider them prey.
The majority of tetra species are in the midrange size and typically don’t get longer than 3 inches. This group includes black skirt, bleeding heart, Buenos Aires and Congo tetras. Large tetras, such as long-finned and bucktooth tetras can grow to 4 or 5 inches. Tetras in the mid-to-large range often do quite well with smaller types of cichlids like African cichlids and angel fish.