Swordtails are one of the most common and popular aquarium fish in the world for all the right reasons. They come in an array of colours, look super unique, and are quite easy to take care of. Where most swordtail strains are super bright, the black swordtail puts a very unique and bold spin on this fish. The most loved feature about this fish is the long extension seen on the tail of the male fish which looks like the blade of a sword. In some cases, the sword can be just as long as the fish itself which is stunning to see.