Yes, two Red Devils can live together in an aquarium if the tank is large enough to provide adequate space for each fish. It is important that each fish has its own hiding place and plenty of room to swim around. Additionally, make sure there are plenty of rocks and decorations inside the tank so they have something interesting to explore. If possible, try to keep these two devils in separate sides of the tank as well. This will help reduce aggression between them and prevent territorial disputes which could lead to harm or even death for one or both fishes.