Blue gourami, glass catfish, khulii loach, cory catfish, bristlenose plecos and white cloud mountain minnows are all potential tankmates for a betta fish. When choosing companion fish, consider the temperament of the individual betta and the aquarium conditions best suited to each potential tankmate.
When searching for companion fish for a betta, the pet owner needs to evaluate the size of the environment. The betta, or Siamese fighting fish, requires 5 gallons of personal water space. Adding companion fish to the aquarium increases the size of tank required. Certain companion fish, such as plecos, grow quite large, depending on their environment. In a large tank, these companions may grow too large to live alongside the betta, so avoid this type of companion in a very large aquarium. Also consider the water environment. Different fish thrive in varying temperature ranges, so choose fish with complementary environmental and nutritional needs.
Consider behavioral habits when selecting a tankmate as well. Betta fish react aggressively to fish breeds that tend to nibble, so avoid these breeds entirely. Also avoid large, colorful fish that intimidate betta fish, encouraging aggression. Bottom-dwelling fish breeds, such as plecos, cories and loaches, make the ideal companions for bettas under most conditions. After deciding on a companion fish breed, purchase fish that live naturally in schools in quantity of at least six, though larger schools may be appropriate in larger tanks.