The Betta fish is probably the second most popular fish kept, after Goldfish. The Betta Splendens is a favorite because of its beauty, its long fins and because bettas are relatively easy to care for. Betta fish are called the Siamese Fighting Fish because of its behavior towards other males of the same species. You cannot keep two or more males in the same tank. If more than one male fish are placed in the same tank, they will fight until only one of them remains.