Mollies are a species of tropical fish that prefer warm temperatures in their tank. They like water between 76-79°F (24-26°C). Keeping the temperature at this range will help the molly live a healthy and happy life, as well as encourage breeding when you want to increase your population. It's important to maintain stable temperatures in your aquarium, so check the thermometer regularly and adjust if necessary. You should also make sure there is enough space for them to swim around freely without overcrowding the tank.