The Sailfin Molly, also known as the Yucatan Molly, is a stunning and active fish, famous for the male's enormous, fan-like dorsal fin which it displays to impress females. These are not small fish and can grow quite large, so they require a spacious aquarium from the outset—do not plan on keeping them in a small tank. They are constantly on the move, exploring the top and middle levels of the tank with impressive speed. While they are generally peaceful, males can be territorial with each other, so it's best to keep one male with several females to prevent stress and fighting. They are not demanding eaters and will accept a wide variety of foods, but they have a particular need for vegetable matter in their diet, and will enjoy grazing on any algae in the tank. To keep them healthy, they need warm water that is hard and alkaline. They feel their best when a small amount of aquarium salt is added to create slightly brackish conditions, which mimics their natural home in Mexico. Because they are active and eat a lot, they produce a fair amount of waste, so a good filter and regular water changes are essential to keep their home clean and healthy.